Lithium storage mechanisms and kinetics in MOF-based anodes: from pristine frameworks to derived materials for high-performance lithium-ion batteries

1 Introduction

Among all concurrent battery technologies, lithium-ion batteries (LIBs) remain the dominant energy storage system owing to their uniquely high energy density, long cycle life, and mature manufacturing technologies (Gao Y. et al., 2022). However, the conventional graphite anode, with a relatively low theoretical specific capacity of 372 mAh g^-1, is prone to inducing short cycle lives and serious safety concerns (Wu et al., 2019), thus fundamentally limiting further improvements to LIBs. Consequently, extensive efforts have been made to develop alternative anode materials with higher lithium storage capacities along with enhanced electrochemical performance. However, achieving both high capacity and long-term stability in next-generation anode materials remains a critical challenge due to complex lithium storage mechanisms and structural instability during cycling.

The lithium storage behaviors of the anodes play a central role in determining the electrochemical performance of lithium-ion batteries (Lu J. et al., 2018). Fundamentally, the capacity of a battery electrode and the energy density of LIBs are closely related to the number of electrons transferred during redox reactions (Gao and Yang, 2010), which is directly associated with the amount of lithium that can be reversibly stored within the electrode material. Meanwhile, efficient and uniform lithium storage requires rapid Li⁺ transport within the electrode structure and stable insertion-extraction pathways during repeated electrochemical cycling. When lithium ions can migrate smoothly and reversibly into and out of the host structure, the electrode can maintain stable redox activity with minimal structural degradation. Hence, abundant redox sites, large lithium storage capacity, and stable lithium storage pathways are three critical factors determining the performance of anode materials.

Lithium storage in conventional graphite anodes occurs through an intercalation mechanism, in which lithium ions are reversibly inserted into the layered graphite structure to form LiC₆. With a wide range of high-capacity candidates being exploited and researched, many emerging high-capacity anode materials store lithium through alternative mechanisms, such as alloying reactions (Fang et al., 2019; Lübke et al., 2017; Ye et al., 2023) or conversion reactions (Lu Y. et al., 2018; Yu et al., 2016), which can deliver significantly higher capacities exceeding 1000 mAh g^-1. However, their practical implementation is hindered by severe electrochemical and structural challenges. For instance, the extended lithiation/delithiation process can cause catastrophic volume change (∼300%) of silicon anodes (McDowell et al., 2012; Zhang, 2017), leading to particle pulverization, unstable solid-electrolyte interphase (SEI) formation, and progressive loss of electrical contact within the electrode.

In recent years, metal-organic frameworks (MOFs), a class of crystalline porous compounds assembled from metal ions or clusters that coordinate to organic ligands (Yuan et al., 2018), have emerged as a highly promising class of materials for next-generation lithium-ion battery anodes, owing to their unique structural tunability and chemical versatility. As shown in Figure 1A, the annual amount of publications on MOF-based anode materials for lithium-ion batteries has increased steadily over the past decade, highlighting the increased recognition of MOF-based materials as a key platform for addressing the limitations of conventional anodes. However, the complex lithium storage mechanisms and kinetic behaviors in MOF-based anodes remain insufficiently understood, which limits the rational design of high-performance electrode materials. MOFs possess tunable pore structures, exceptionally high surface areas, and abundant accessible active sites enabled by their versatile chemical compositions (Cai et al., 2019; Zhao et al., 2019). These features allow MOFs to serve not only as electrochemically active anode materials for lithium storage, but also as precursors for the synthesis of functional derivatives through controlled thermal or chemical transformations (Song et al., 2023; Sun et al., 2015; Tan et al., 2020; Weng et al., 2019). Consequently, both pristine MOFs and MOF-derived materials have been widely investigated as LIB anodes with various lithium storage behaviors. In pristine MOFs, lithium storage may occur through ligand-based intercalation, redox reactions at metal centers, or surface-dominated pseudocapacitive processes. In contrast, MOF-derived materials typically employ conversion reactions, alloying/de-alloying processes, or host-storage within porous carbon matrices. Table 1 provides a summary of representative MOF-based anode materials and their lithium storage mechanisms in recent studies. These mechanisms enable MOF-related materials to exhibit incredible potential to improve the electrochemical performance of LIBs, including capacity, Coulomb efficiency, rate capability, and long-term cycling stability. Therefore, understanding the fundamental lithium storage mechanisms in MOF-based anode materials is essential for further rational design of high-performance lithium-ion batteries.

TABLE 1. MOF-based LIB anodes in recently published works.

Unlike previous reviews that mainly focus on material synthesis or performance comparison, this work emphasizes a mechanism-oriented perspective, systematically linking lithium storage pathways with structural features and electrochemical behavior in MOF-based LIB anodes. Figure 1B shows the structure of this review. First, lithium storage behaviors of pristine MOFs are summarized, focusing on ligand-based intercalation, metal-center redox reactions, and their synergetic combinations. Then, major lithium storage mechanisms in MOF-derived materials are discussed, spanning conversion reactions, alloying processes, and carbon-matrix-based storage. Pseudocapacitive behaviors that are able to promote lithium storage kinetics are then examined, since they are of great importance in facilitating all the storage mechanisms of both pristine-MOF-based and MOF-derived anodes. Furthermore, key characterization techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning/transmission electron spectroscopy (SEM/TEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, operando X-ray diffraction (XRD), electrochemical characterizations, and density functional theory (DFT) calculations, are reviewed to elucidate the discovery and analysis of specific mechanisms. Finally, future perspectives for MOF-based anodes are discussed, aiming to provide an outlook for the development of next-generation high-energy lithium batteries. This review aims to bridge the gap between structure, lithium storage mechanisms, and electrochemical performance in MOF-based anodes, providing insights into material design for high-performance lithium-ion batteries.

2 Lithium storage mechanisms in pristine MOFs

The coexistence of metal nodes and redox-active organic ligands in MOFs provides multiple electrochemical reaction pathways for lithium storage, including lithium intercalation enabled by the organic ligands, redox reactions at metal centers, and surface-dominated pseudocapacitive processes. Ideally, many anodes combine more than one mechanism, leading to further improved performance. Figure 2 provides an overview of the lithium storage mechanisms in pristine MOF anodes.

2.1 Ligand-based intercalation

Intercalation is a typical topotactic reaction, in which lithium ions are reversibly inserted into the host structure without significant disruption of the crystal framework, which is fundamental for rechargeable lithium batteries (Whittingham et al., 2018). During this process, the host lattice undergoes only minor structural changes, such as slight expansion of interlayer spacing, while maintaining its overall structural integrity (Zhou et al., 2021). In MOF-based anodes, the organic linkers, endowed with rich functional groups like aromatic rings, and specific electron structures, provide favorable binding sites for lithium ions. Compared with other mechanisms, intercalation involves minimal volume change and structural rearrangement, thereby enabling reversible lithium storage and improved battery performance.

In 2016, Hu et al. successfully synthesized a cobalt-based MOF, Co-1,4-benzenedicarboxylate (Co-BDC), via a one-pot solvothermal method, and investigated its potential as a lithium-ion battery anode (Hu et al., 2016). Since the ex-situ XPS and FTIR analyses revealed that the cobalt ions in Co-BDC remain in the Co²⁺ state throughout the charge-discharge processes, the Li ions were therefore deduced to insert directly into the organic moieties, which feature abundant carboxylate functional groups and aromatic rings. In particular, the deprotonated carboxylate groups (–COO^–) interact with Li⁺ via Coulombic attraction and the high electronegativity of oxygen atoms during lithiation. Simultaneously, the aromatic rings of the BDC ligands provide additional storage sites via cation-π interactions with the delocalized electron clouds, thereby further expanding lithium storage capacity and activating electron transfer. This dual-site storage mechanism facilitated exceptional electrochemical performance, delivering a discharge capacity as high as 1963.6 mAh g^-1 at 100 mA g^-1 and exceptional cycle stability, with a capacity retention rate of 70.7% after 100 cycles at 200 mA g^-1. More intriguingly, the charge-transfer impedance remained small and nearly unchanged throughout extensive cycling, indicating a rapid solid-state Li⁺ diffusion rate enabled by a smooth insertion into and release from the lithium storage space of the BDC ligand. A similar ligand-dominated lithium storage behavior was reported by Gong et al., who investigated a series of Mn(II) and Co(II) MOFs constructed from mixed azide and carboxylate ligands (Gong et al., 2017). Compared with Hu et al.’s work, they have developed an optimized structure for the anode by designing a pillared-layer structure for the 3D-MOF, creating a stable framework with expanded interlayer spacing, which is intrinsically ideal for extensive lithium storage by providing robust Li⁺ diffusion pathways. During lithiation, soft X-ray absorption spectroscopy and nearly identical electrochemical performance of the isomorphous Co(II) and Mn(II) frameworks confirmed no metal conversion reaction occurrence, while the azide ions and aromatic rings on the ligand served as active lithium insertion sites. As expected, the pillared-layer MOFs exhibited reversible capacities of approximately 580–595 mAh g^-1 with good cycling stability. Furthermore, in 2020, Yin et al. synthesized Ni-Mn-BPTC-e-MOF using ethanol, employing a ligand with versatile coordination modes (Yin et al., 2020). During lithiation, each carboxylic group coordinates with one Li⁺ ion, while each aromatic ring coordinates with six Li⁺ ions via cation-π interaction. With a capacity of 1380 mAh g^-1 at 100 mA g^-1, this MOF also exhibits excellent anode performance, owing to fast Li⁺ transport channels and structural stability.

Beyond the electron transfer enabled by cation-π interaction, the functional groups of the organic ligands can also participate in redox reactions with lithium ions, thereby enhancing the anode’s capacity. A representative example was provided by the work of Zhou et al., who designed a series of redox-active azo-based MOFs, with 1,2-bis(3,5-dicarboxyphenyl)diazene-oxide (H₄OL) as ligands, as anode materials for lithium-ion batteries (Zhou et al., 2019). As revealed by FTIR, during lithiation, the azo groups (–N=N–) and the carbonyl groups (C=O) interact with lithium ions and are reduced to the lithiated state, while the deprotonated carboxylate groups and the negatively charged oxygen atoms serve as additional sites for lithium storage. With the contribution of azo-based redox chemistry, extended lithium storage capacity, and a stable framework, MOFs deliver high initial discharge capacities (up to 1560.6 mAh g^-1 for Ni-MOF) and maintain excellent long-term cycling stability over 500 cycles. More recently, Zhang et al. developed a layered 2D Ni-MOF as a high-performance LIB anode material (Zhang et al., 2023). In their work, the 2D framework, characterized by distorted octahedral Ni²⁺ centers bridged by tfbdc organic ligands, provides open interlayer channels that significantly facilitate lithium ion diffusion. Similar to the Co-BDC system, ex-situ XPS and CV analyses confirmed that the Ni²⁺ metal centers remain electrochemically inactive throughout cycling, whereas the lithium storage is driven by the reversible redox activity of carbonyl groups on the organic ligand. During lithiation, the C=O bonds in the carbonyl groups are reduced to C–O–Li, thereby forming enol structures and facilitating electron transfer. This synergistical redox mechanism, supported by high structural stability and low charge-transfer resistance, enables the Ni-MOF anode to deliver a high reversible capacity of 765 mAh g^-1 at 100 mA g^-1 with 97.9% capacity retention after 140 cycles.

The works reviewed above show that the MOF ligand itself can boost the performance of lithium-ion batteries by redox reactions and efficient lithium storage. The lithium ions are reversibly accommodated within the organic ligands through interactions such as coordination with heteroatom-containing functional groups, cation-π interactions with aromatic systems, or reversible redox reactions on conjugated linkers. Nevertheless, the structural stability of some MOFs under prolonged cycling remains a concern, while lithium storage that relies solely on ligand-Li interactions or ligand-centered redox processes is still often insufficient to support the demanded extensive electron transfer and high reversible capacity. Therefore, increasing attention has been directed toward activating the redox activity of metal centers within MOF frameworks, thereby introducing additional electron-transfer pathways and significantly enhancing lithium storage capability. This metal-centered redox mechanism will be discussed in the following section.

2.2 Metal-center redox reactions

Beyond ligand-dominated systems, plenty of MOFs achieve superior capacity through direct redox conversion of metal nodes. Specifically, metal nodes that are thermodynamically stable and possess accessible oxidation states, in which transition metals such as Fe, Co, and Ni are included, are capable of participating in redox reactions (Calbo et al., 2019). As a result, MOFs constructed with these redox-active metal nodes can provide substantial electrochemically active reaction sites, thereby promoting electron transfer and significantly boosting the overall anode capacities.

The MOF utilized by Baskoro et al., in 2021, Pb-BTC, serves as a remarkable example for metal-center-redox-dominated lithium storage (Baskoro et al., 2021). As confirmed by ex-situ XPS analysis, the lead metal node reversibly reduced from Pb²⁺ (Pb–O) to Pb⁰ during delithiation, which is subsequently oxidized back to the original Pb²⁺ state during the charging process. Remarkably, the anode capacity increased after 100 charge-discharge cycles, attributed to additional redox reactions of Pb⁴⁺ (O–Pb–O) generated during cycling. The Pb⁴⁺ ions underwent staged redox processes in the subsequent cycles, being consecutively reduced to Pb²⁺ and ultimately to Pb⁰, which contributes further to excessive electron transfer. Synergized with a non-dominating redox reaction between Li⁺ and the carboxylic groups in the BTC ligand, the framework exhibits exceptional structural reversibility and cycling stability, delivering a high reversible capacity of 625 mAh g^-1 and maintaining 445 mAh g^-1 even after 1000 cycles. Despite such promoted battery performance, the usage of toxic Pb in this work is not ideal in terms of sustainability. Non-toxic metal nodes that still possess similar redox ability should be further sought.

Bimetallic metal nodes have been further employed in MOF structures to enhance lithium storage performance. Such a strategy not only increases the density of redox-active sites but also introduces synergistic interactions between different metal centers, which can facilitate electron transfer and promote their participation in reversible redox reactions. In the exemplary work of Dai et al., the researchers constructed a TCPP(Fe)-Ni MOF nanofiber, in which both the Ni²⁺ nodes and the Fe³⁺ centers embedded within the porphyrin rings serve as electrochemically active sites for redox reactions (Dai et al., 2023). In particular, the XPS revealed a strengthened oxidation activity of Ni²⁺ relative to single-node Ni-TCPP, owing to the introduction of Fe³⁺; meanwhile, the chelation between Fe³⁺ and the porphyrin rings not only reinforces the structural integrity of the framework but also provides additional redox pathways. As a result, the TCPP(Fe)-Ni anode delivers a superior reversible capacity of 950 mAh g^-1 at 100 mA g^-1, significantly outperforming its monometallic counterparts and demonstrating the potential of bimetallic strategies in enhancing the electrochemical performance of MOF-based anodes. This work highlights that the incorporation of a second metal center can effectively modulate the electronic structure of the primary active site, thereby enhancing its redox activity and enabling additional electron transfer pathways. Li et al. constructed another bimetallic MOF nanosheet, Co_*x*Fe_1-*x*-MOF, using BDC as the ligand (Liu et al., 2025). During lithiation, the Co²⁺ and Fe²⁺ metallic nodes are reversibly reduced to Co⁰ and Fe⁰, respectively, and restored to their original states during delithiation. Notably, compared to the corresponding single-metallic-node MOFs, the bimetallic setting synergistically enhanced electron conductivity and lithium diffusion. Owing to a shortened diffusion path brought by the layered nanosheet structure and the bimetallic redox reactions, a highly reversible initial discharge capacity of 2050.3 mAg g^-1 at 100 mA g^-1 and a retained capacity of 1132 mAh g^-1 after over 200 cycles were reached.

In practical MOF-based anodes, high lithium storage capacity is typically achieved through the combined contribution of ligand-based lithium storage and redox reactions at metal nodes. Li et al.’s work serves as an example showcasing a sophisticated integration of metal-centered conversion and ligand-based multi-electron redox (Li et al., 2025). In their MOF, Co-NTTA, a multistep insertion of Li⁺ into the electrochemically active carboxylate (O–C=O) and amido functional groups (NH–CO) of the ligand occurs during lithiation, contributing 12 and 3 electrons per structural unit through redox reactions, respectively. In the meantime, the larger conjugated π-surfaces of the selectively activated aromatic rings of the ligand offer the transfer of 6 electrons per unit via reversible cation-π interaction. Beyond ligand intercalation, the Co active centers are reduced from Co²⁺ and Co³⁺ to metallic Co nanoparticles, transferring 30 electrons per structural unit. Enabled by the total transfer of 51 electrons per unit and a large lithium storage capacity and robust structural stability, the Co-NTTA anode exhibited an extraordinary reversible discharge capacity of 1390 mAh g^-1 at 50 mA g^-1, pushing the boundaries of theoretical capacity in MOF-based energy storage systems. Additionally, the MOF developed by Gaber et al., Fe-Tp, also presented synergetic effects of multiple active sites (Gaber et al., 2024). The Tp ligand enables interactions between lithium ions and high-density lithiophilic sites, including their reversible binding to oxygen atoms, reduction of the –C=O units, and Li⁺-π interactions with phenolic functional groups. Simultaneously, the Fe³⁺ metallic nodes are reduced to Fe²⁺ during lithiation, further contributing to electron transfer. As a result, the battery achieved a high specific capacity of 1447 mAg g^-1 at 100 mA g^-1 and 89% of cyclic stability after 500 cycles at 1.0 A g^-1. Furthermore, the green synthesis of CoZn-MOF using BDC as the ligand by Wang et al. demonstrates a successful combination of ligand interactions and bimetallic-node redox during lithium storage, while sustainability is taken into account (Wang et al., 2024). In their work, lithium storage mainly depended on the interaction between Li⁺ and the aromatic rings and carboxylate functional groups on the ligand, while Co²⁺ and Zn²⁺ are reversibly reduced to Co⁰ and Zn⁰ during lithiation. In a water system, the CoZn-MOF anodes delivered an impressive specific capacity of 2774 mAh g^-1 at 100 mA g^-1 and excellent cycling stability. Taken together, these representative studies highlight that the integration of ligand-based storage and metal-centered redox reactions enables multi-electron transfer processes, which are key to achieving exceptionally high lithium storage capacities in MOF-based anodes. In particular, the coexistence of multiple active sites, including functional groups, conjugated π-systems, and redox-active metal centers, allows for synergistic utilization of both organic and inorganic components, significantly enhancing overall electrochemical performance. Compared with single-site storage systems, such multi-site, multi-electron mechanisms provide a more efficient pathway for maximizing charge storage.

Nonetheless, both ligand intercalation and metal-node redox require lithium insertion into the bulk framework, which typically involves diffusion-limited processes that limit the electrode’s rate capability. Moreover, extensive redox reactions at metal centers and repeated intercalations of Li⁺ with the organic ligand may lead to framework distortion or amorphization during prolonged cycling. To overcome these limitations, pseudocapacitive lithium storage, where fast surface or near-surface redox reactions enable rapid charge transfer and improved rate performance, has been investigated by researchers. Figure 3 provides a summary of key performance results of pristine MOF anodes in representative works, and Table 2 summarizes the application of pristine MOFs as LIB anodes, covering lithium storage mechanisms and battery performance.

TABLE 2. Summary of selected pristine MOFs as LIB anodes.

3 Lithium storage mechanisms in MOF-derived materials

In a number of recent studies, MOFs are also used as sacrificial precursors to derive metal-based active phases and conductive carbon matrices. Compared with pristine MOFs, MOF-derived materials usually undergo substantial structural and compositional transformation during various post-treatment processes, resulting in the formation of secondary hollow porous nanomaterials, including metal carbides, metal oxides, metal sulfides, porous carbon materials, and their hybrid composites (Liu et al., 2022). These derived structures generally exhibit higher electrical conductivity, improved structural stability, and richer electrochemically active sites, thereby enabling more efficient lithium storage (Zhang et al., 2019). The lithium storage behaviors of MOF-derived materials involve conversion reactions, alloying processes, and lithium adsorption at defect-rich carbon surfaces or porous interfaces. Figure 4 offers an overview of the lithium storage mechanisms in MOF-derived LIB anodes.

3.1 Conversion reactions

Conversion reactions are particularly common in derived metal compounds such as metal oxides, sulfides, phosphides, and selenides. The conversion reaction between lithium and nanosized transition metal oxides can be expressed by Equation 1 below (Yu et al., 2016):

M x O y + 2 y Li + + 2 y e ‐ ↔ x M 0 + y Li 2 O M = transition metals (1)

Similar conversion reactions can also occur in other MOF-derived metal compounds, although the final lithiated products and stoichiometric relationships depend on the anion species. By Equation 1, the conversion reaction allows the storage of up to 2y lithium ions per formula unit of metal oxide, accompanied by amorphization and substantial volume expansion of the host material; upon complete lithiation, the transition metal oxide is reduced to nanoscale metal clusters embedded in a Li₂O matrix (Yu et al., 2016). Nonetheless, the nano-size and hollow/porous structure derived from MOFs can offer more active sites, shortening the distance of ion transport and buffering the volume expansion (Tan et al., 2020), making it ideal for LIB anodes.

A representative example of conversion-type lithium storage in MOF-derived metal oxides was reported by Tian et al., who prepared porous Co₃O₄ hollow tetrahedra using MOFs as self-sacrificing templates (Tian et al., 2015). In this system, the redox peaks at 1.07 and 2.08 V were assigned to the reversible conversion between Co₃O₄ and metallic Co, accompanied by the formation/decomposition of Li₂O, confirming a typical conversion mechanism. Also, the high Coulombic efficiency after the second cycle indicated a high reversibility of the conversion reaction, and their battery demonstrated a remarkable reversible capacity of 1196 mAh g^-1 at 50 mAh g^-1.

Furthermore, during the synthesis of MOF-derived metal compounds, the organic ligands in MOFs can transform into a carbon matrix, which plays an important role as a conductive network to facilitate electron transfer (Xiao et al., 2023) and generate synergetic effects with the metal compounds. Notably, the carbon framework can also provide overall structural robustness for the anode, thereby alleviating volume expansion during lithiation and delithiation. Therefore, many works integrate carbon composite with the derived metal compounds. In 2016, Chen et al. prepared porous Fe₃O₄/C octahedral nanostructures, in which Fe₃O₄ was encapsulated by carbon layers and underwent a typical conversion reaction (Fe₃O₄ + 8Li⁺ + 8e^– ↔ 3Fe + 4Li₂O) (Chen et al., 2016). The researchers showed that Fe nanodomains were successfully embedded in the Li₂O matrix during lithiation, while the Fe₃O₄ structure was restored during delithiation. More importantly, the measured capacity of their battery (861 mAg g^-1 @100 mA g^-1) exceeded the theoretically predicted capacity (649 mAg g^-1 @100 mA g^-1), which was attributed to the synergetic effect between Fe₃O₄ and carbon. The porous octahedral architecture and carbon matrix helped alleviate volume change, suppress aggregation, and maintain reaction reversibility as well. Similarly, Peng et al. reported mesoporous Mn₃O₄/C microspheres derived from a Mn-based MOF, in which the composite design was introduced specifically to address the severe volume expansion and poor conductivity of Mn₃O₄ (Peng et al., 2017a). The mesoporous microspherical structure provided a large accessible surface area and shortened ion-transport pathways, thereby improving electrochemical reversibility and facilitating repeated conversion. Comparable effects were also observed in sulfide systems. Yao et al. synthesized a flower-like FeS/C composite in which FeS nanoparticles were encapsulated by carbon and assembled into a stable laminated structure (Yao et al., 2019). Since FeS typically suffers from large volume expansion and low conductivity during conversion-based lithiation/delithiation, the carbon-wrapped flower-like architecture played a direct role in shortening electron/ion transport pathways, confining nanoparticle growth, and restraining structural degradation, thus promoting more stable cycling. Their battery delivered an initial discharge capacity of 994.4 mAh g^-1 and a maintained capacity of 768.7 mAh g^-1 at 100 mA g^-1 after 100 cycles. These studies indicate that, in MOF-derived single-metal composites, the carbon component does not merely enhance conductivity but, more fundamentally, improves the reversibility, kinetics, and mechanical tolerance of conversion reactions during repeated cycling.

Beyond single-metallic compounds, multimetallic compounds can also be prepared from heterometallic MOFs as precursors, delivering better electrochemical performance than their single-metal counterparts due to the synergistic effect between metal species (Tan et al., 2020), especially when composited with carbon. For instance, Gong et al. demonstrated that bimetallic design can substantially improve the reversibility of conversion reactions in MOF-derived mixed oxides (Gong et al., 2021). In their Co-Mn-O/C hollow spheres embedded in an amorphous carbon matrix, ex situ XRD confirmed that the lithiation process involved the reduction of CoMn₂O₄, Mn₂O₃, and Mn₃O₄ into metallic Co/Mn, accompanied by the formation of Li₂O; these oxide phases reappeared after charging, indicating a reversible conversion process. Notably, compared to single-metal Mn-O/C, the incorporation of Co helped to provide a smaller hollow sphere diameter and larger interior porosity, thereby facilitating a faster Li⁺ diffusion and resulting in an easier attachment of Li ions onto the inner surface of Co-Mn-O/C; and similar to what has been discussed above, the continuous amorphous carbon matrix provided high mechanical support for the Co-Mn-O nanograins embedded within it. Such a combination of derived bimetallic compounds and carbon matrices delivered a specific capacity as high as 1088.5 mAh g^-1 at 1000 mA g^-1 after 600 cycles. A similar enhancement effect was observed in the MOF-derived CoNiSe₂/C nanododecahedrons reported by Han et al. (2024). In their work, CoNiSe₂ was reduced to Co, Ni, and Li₂Se during discharge and re-formed upon charging, indicating great reversibility of the conversion reaction. Remarkably, the synergistic effect of bimetallic selenides, well-defined porous nanodecahedral structures, and stable carbon networks collectively contributed to reduced volume change, increased Li⁺ storage active sites, and shorter Li⁺ diffusion paths, eventually leading to a high specific capacity of 549.9 mAh g^-1 at 1000 mA g^-1 after 1000 cycles. Further examples of MOF-derived bimetallic compounds included the α-MnSe/C composite (Li et al., 2019) and the NiCo₂O₄ nanofiber arrays (Babu et al., 2023), in which the carbon framework facilitated Li⁺ transport and suppressed the shrinkage and pulverization of the active material, thereby benefiting conversion lithium storage. Overall, these results demonstrate that the integration of multimetallic compositions and carbon matrices effectively enhances the reversibility of conversion reactions, improves structural stability, and facilitates lithium-ion transport, thereby leading to significantly improved electrochemical performance compared to single-metal systems.

Apart from the regular carbon obtained from the MOF ligands, Zou et al. further showed that carbon-assisted regulation of conversion-dominated lithium storage can also be achieved by incorporating carbon nanotubes (Zou et al., 2017). In their MOF-derived porous ZnO/MWCNTs nanocomposite, ZnO polyhedra constructed from nanosized subunits were intertwined with inserted MWCNTs, producing a hierarchical porous architecture with improved structural integrity and charge transport. Since ZnO typically suffers from severe volume change and poor electrical conductivity during lithiation/delithiation, the introduction of MWCNTs played a dual role: it enhanced electronic conductivity and accelerated reaction kinetics, while also stabilizing the ZnO framework against pulverization and aggregation during repeated cycling. In addition, the porous polyhedral structure and concave surface provided extra void space to buffer the large strain associated with the conversion/alloying process. As a result, the ZnO/MWCNT composite exhibited more favorable electron transport, faster Li⁺ diffusion, and better cycling stability than bare ZnO, presenting a reversible capacity of 419.8 mAh g^-1 at 200 mA g^-1 after 100 cycles. Similarly, reduced graphene oxide (rGO) can also serve as a composite basis to enhance anode performance Liu et al. synthesized nitrogen-doped ZnSe polyhedra encapsulated by rGO, in which lithium storage involved the conversion of ZnSe into LiZn and Li₂Se during discharge, followed by the reconstruction of ZnSe upon charging (Liu et al., 2018). The MOF-derived polyhedral framework, nitrogen doping, and conductive rGO coating collectively promoted a more reversible conversion process by increasing active sites, accelerating charge transport, and suppressing structural degradation during cycling. More recently, Zheng et al. synthesized CoS₂-MnS and also composited it with rGO, in which the conversion reactions delivered a superior capacity of 1327 mAh g^-1 at 100 mA g^-1 after 100 cycles, further proving the effect of compositing MOF-derived metal compounds with carbon-based materials (Zheng J. et al., 2021). These results demonstrate that the incorporation of external carbon frameworks (e.g., CNTs and graphene oxide) into MOF-derived materials effectively enhances electronic conductivity, buffers volume changes, and improves the reversibility of conversion/alloying reactions, thereby leading to significantly improved lithium storage performance.

Beyond pristine carbon frameworks, several studies have revealed the functions of heteroatom-doped carbon composites, which can further regulate conversion-type lithium storage by modifying the interfacial electronic structure and ion-transport behavior. Zhang et al. reported ZnO nanoparticles coated with thin N-doped carbon layers and hybridized with carbon nanotubes, in which the optimized hybrid structure exhibited much better cycling stability than bare ZnO- or carbon-only counterparts (Zhang et al., 2017). The authors attributed this behavior not only to the conductive CNT network and porous architecture, but also to the N-doped carbon coating, which effectively buffered the volume expansion of ZnO during repeated alloying/dealloying and maintained the integrity of the porous hybrid framework. Their battery delivered an excellent specific capacity of 850 mAh g^-1 at 100 mA g^-1, which was higher than the calculated theoretical capacity, along with excellent cycling stability. As an improvement, Li et al. synthesized a MOF-derived Cu₂S@N,S co-doped carbon heterostructure, in which the heteroatom co-doping and heterogeneous interfacial modulation significantly enhanced electrical conductivity, accelerated Li⁺ diffusion, and strengthened charge interaction at the active interface, thereby promoting the reversible conversion of Cu₂S and improving long-term cycling stability (Li et al., 2023). In summary, heteroatom-doped carbon frameworks can effectively regulate conversion-type lithium storage by tuning the interfacial electronic structure, enhancing electrical conductivity, and facilitating ion transport, thereby improving reaction reversibility and cycling stability.

Non-carbon composite MOF-derived metal compounds have also been shown to be strong candidates for lithium battery anodes in several studies, as the stabilization of conversion-type lithium storage can be achieved through synergistic coupling between different inorganic phases. For example, Cai et al. reported a porous ZnO/ZnFe₂O₄ hybrid nanostructure derived from a Prussian blue analogue template (Cai et al., 2017). The first lithiation process involved the reduction of Fe³⁺ and Zn²⁺ to Fe⁰ and Zn⁰, while during recharging, the anodic sweep revealed the re-oxidation of metallic Zn and Fe, indicating a coupled conversion-alloying mechanism with good reversibility after the initial cycle. More importantly, the porous hybrid structure not only provided sufficient void space to accommodate volume expansion but also enabled ZnO to act as a buffer domain that spatially separated the highly electroactive ZnFe₂O₄ nanophase, thereby suppressing aggregation and relieving crystal strain during repeated cycling, delivering a high specific capacity of 704 mAh g^-1 at 200 mA g^-1 after 200 cycles. A similar effect was observed in the self-assembled ZnO/Co₃O₄ nanocomposite clusters reported by Zhu et al., where both Zn and Co species participated in reversible redox reactions after the initial activation cycle (Zhu et al., 2015). The authors attributed the enhanced lithium-storage performance to the porous cluster architecture, which shortened ion/electron transport pathways and mitigated the severe volume change associated with conversion reactions, and to the synergistic effect between ZnO and Co₃O₄. These results suggest that, even without carbon integration, rational phase coupling in MOF-derived hybrid metal compounds can substantially improve the reversibility, structural tolerance, and kinetic accessibility of conversion-dominated lithium storage.

3.2 Alloying/de-alloying reactions

Alloying reactions also play an important role in lithium storage for MOF-derived materials, particularly in systems containing alloy-active elements such as Sn, Zn, Sb, and Bi (Gopinadh et al., 2024). Typically, the alloying and de-alloying reaction of a metal element in the LIB anode with the lithium ion can be described by Equation 2 below:

M + x Li + + x e ‐ ↔ Li x M M = transition metals (2)

Pure alloying reactions do not involve the reductive decomposition of metal compounds into metallic species, as occurs in conversion reactions. Instead, they proceed through the electrochemical alloying of lithium with alloy-active metals. Theoretical and interfacial studies on Li-Sn and Li-In alloys suggest that certain alloy phases can also facilitate fast Li-ion transport and lower interfacial resistance, which is advantageous for reaction kinetics and rate capability (Qu et al., 2020). Also, Baskoro et al. showed that the alloying mechanism can also boost the capacity of batteries by providing additional lithium storage reactions (Baskoro et al., 2021).

Representative alloying-type lithium storage in MOF-derived materials has been revealed by MOF-derived alloys. The NiSb alloy nanoparticles were synthesized and embedded in carbon hollow spheres using a Ni-MOF precursor by Yu et al. (2017). In this work, the MOF-derived hollow architecture of the alloy-carbon composite provided additional void space, preserved structural integrity, and facilitated rapid electron/ion transport. More essentially, the alloying/dealloying process between Sb and Li served as the dominant storage mechanism, and contributed to a high rate capability (210 mAh g^-1 at 2000 mA g^-1). Together, the structural advantages and the assistance of Li-Sn alloying reaction delivered an excellent specific capacity of 497.3 mAh g^-1 at 100 mA g^-1 after 100 cycles.

Beyond MOF-derived pure metal alloys, many MOF-derived metallic compounds exhibit alloying reactions as secondary or coupled storage mechanisms that accompany or follow the initial conversion process, which produces metallic elemental substances that participate in the alloying reactions. Hence, storing lithium by combining conversion and alloying reactions is ideal for lithium battery anodes, and the porous structures of MOF-derived compounds can facilitate the alloying process by providing fast diffusion pathways for the lithium ions. For example, Li et al. reported a series of Sn-MOF-derived products, among which the Sn/SnO@C composite exhibited the best performance (Li et al., 2020). The SnO compound first underwent conversion to generate metallic Sn and Li₂O, after which the resulting Sn further reacted with lithium through alloying to form Li_*x*Sn. While the carbon matrix suppressed volume expansion and enhanced conductivity, the coexistence of rod-like SnO and sphere-like Sn promoted Li⁺ diffusion and led to a smoother alloying reaction between Li⁺ and Sn. Hence, alloying is not an isolated process but a coupled mechanism that follows or accompanies the initial conversion reaction, jointly contributing to high lithium-storage capacity and improved electrochemical performance. Only when lithium diffusion is not hindered can alloying reactions be successfully conducted, thus providing extra lithium storage capacity for the anode. More recently, Duan et al. derived a bimetallic compound, Mn₂SnO₄@C, in which lithium alloying occurred with both Mn and Sn, confirming a typical conversion-alloying dual storage pathway (Duan et al., 2023). This work also demonstrates that the alloying reaction can benefit from structural advantages, as the coexistence of Mn- and Sn-based redox species enabled mutual buffering during cycling, whereas the carbon layer enhanced conductivity, suppressed particle aggregation, and alleviated structural damage caused by the large volume change of the Sn alloying process.

To summarize, alloying reactions can potentially expand lithium storage capacity and boost rate capability for batteries, with the condition that the lithium diffusion is facilitated by the porous structure of MOF-derived compounds and the successful occurrence of conversion reactions. Together with the structural advantages of porous frameworks and carbon matrices, this conversion-alloying synergy effectively enhances lithium storage capacity, reaction reversibility, and structural stability.

3.3 Defect-dominated lithium storage in derived carbon matrices

Although relevant studies remain limited, pure MOF-derived porous carbon matrices can also serve as active hosts for lithium storage rather than merely as conductive supports. In 2017, Peng et al. synthesized a porous carbon material by carbonizing a Cd-based MOF precursor, which exhibited a large specific surface area and a hierarchical pore structure. As a result, the derived carbon anode demonstrated stable lithium storage behavior and good cycling performance, delivering a high capacity of 1285 mAh g^-1 at 300 mA g^-1 after 300 cycles, highlighting the advantages of MOF-derived carbon matrices as host materials for lithium ions (Peng et al., 2017b). Zheng et al. carbonized a 2D Cu-BDC MOF precursor to obtain porous carbon materials with abundant mesopores, high specific surface area, and defect-rich disordered carbon frameworks (Zheng G. et al., 2021). Unlike conversion- or alloying-dominated systems, lithium storage in these derived carbon matrices mainly arose from reversible Li⁺ insertion into carbon layers together with additional surface-controlled charge storage associated with porous structures and active surface sites. The researchers showed that the microstructure of the derived carbon strongly affected the storage behavior: the optimized sample provided shorter lithium-ion diffusion pathways, a larger electrode/electrolyte contact area, and improved the accessibility of lithium-storage sites, thereby delivering good reversibility and cycling stability. The C₅₀₀ anode exhibited a specific capacity of 690.4 mAh g^-1 at 100 mA g^-1, and maintained 210.3 mAh g^-1 after 500 cycles under a current density of 5000 mA g^-1. These results suggest that, in some MOF-derived materials, the carbon matrix itself can make a non-negligible contribution to lithium storage through combined intercalation- and surface-dominated processes.

In conclusion, lithium storage in MOF-derived materials is governed by multiple, often coupled mechanisms that depend on the chemical composition and structural features of the derived products. Table 3 summarizes the reviewed MOF-derived anode materials and their featured lithium-storage mechanisms and battery performance, and Figure 5 provides a summary of the performance results of MOF-derived anodes in representative works. Among all lithium storage mechanisms, conversion reactions are particularly common in derived metal oxides, sulfides, and selenides, which feature porous frameworks and hollow interiors that are ideal for lithium diffusion. In addition, structural engineering, such as carbon compositing, doping integration, and phase coupling, can greatly improve reversibility and mechanical stability during repeated cycling. In alloy-active systems, lithium storage may proceed via alloying, which contributes to high capacity and rate capability under the precondition of unhindered lithium diffusion and successful conversion reactions. Finally, derived carbon matrices can provide supplementary lithium-storage sites through defect-rich surfaces, porous domains, and surface-dominated charge-storage behavior, although relevant works remain scarce. Therefore, the electrochemical performance of MOF-derived anodes is not determined by a single mechanism alone, but rather by the synergistic interplay among bimetallic interactions, conversion, alloying, and carbon-assisted storage processes, together with the ability of the derived architecture to regulate kinetics, reversibility, and structural integrity.

TABLE 3. Summary of selected MOF-derived materials as LIB anodes.

4 Pseudocapacitive behavior and lithium storage kinetics

4.1 Fundamental theory of pseudocapacitance

Pseudocapacitance refers to a charge-storage mechanism that arises from fast, reversible Faradaic reactions occurring at or near the surface of electrode materials (Gupta, 2024). In pseudocapacitive systems, ion storage primarily occurs via rapid surface or near-surface adsorption and redox reactions rather than through slow solid-state diffusion into the bulk structure and interacting with the MOF structure (Fleischmann et al., 2020). As a result, the charge storage process becomes less diffusion-limited and can proceed with much faster kinetics (Wei et al., 2025). Pseudocapacitive behavior bridges the gap between surface-controlled capacitive processes and diffusion-limited battery-type reactions. The stored charge can be described as a continuous function of potential, rather than discrete phase transitions typically observed in conventional intercalation electrodes. This leads to a nearly rectangular cyclic voltammetry (CV) profile, characteristic of capacitive systems, even though Faradaic reactions are involved.

In battery studies, as it is of paramount significance to quantify kinetics and understand pseudocapacitive behavior near the electrodes, CV experiments are usually conducted. In the CV experiments, the current response to the sweep rate varies depending on whether the redox reaction is controlled by ion diffusion (Jiang and Liu, 2019). The normalization formula for CV kinetics analysis is shown in Equation 3 below (Wang et al., 2007):

i V = k 1 v + k 2 v 1 / 2 (3)

In this equation, V is the fixed potential, v is the CV sweep rate (in mV s^-1), and the coefficients k ₁, k ₂ correspond to the surface capacitive effects and the diffusion-controlled process, respectively. Determining k ₁ and k ₂ can help us understand the percentage of contribution from capacitive and diffusion parts. Another formula characterizing the CV data at various sweep rates is shown in Equation 4 (Lindström et al., 1997):in which i is the measured current, obeying a power-law relationship with the sweep rate v. Quantitatively, b = 0.5 indicates a diffusion-controlled process, while b = 1.0 represents a surface-controlled capacitive process. Values between 0.5 and 1.0 suggest a combination of both mechanisms, with a b closer to 1.0 corresponding to a greater contribution from the capacitive behavior. These kinetic analysis methods are widely used in lithium-ion battery studies to distinguish pseudocapacitive contributions from diffusion-controlled lithium storage, thereby explaining the batteries’ extinguished rate capabilities.

i = a v b (4)

It is worth noting that the capacitive contribution generally increases with increasing scan rate. This behavior originates from the intrinsic kinetic differences between surface-controlled and diffusion-limited processes. At low scan rates, lithium ions have sufficient time to diffuse into the bulk of the electrode, leading to a significant contribution from diffusion-controlled storage (Gowdhaman et al., 2023). In contrast, at high scan rates, the time scale of the electrochemical process becomes too short for long-range ion diffusion, and thus charge storage is dominated by fast surface or near-surface reactions, resulting in a higher apparent pseudocapacitive contribution (Dupont and Donne, 2016).

Figure 6 is a schematic overview of pseudocapacitive behaviors in MOF-based LIB anodes. Nevertheless, one should note that the pseudocapacitive behavior is not a new lithium storage mechanism. Instead, it reflects the kinetic characteristics of existing storage processes, such as ligand-based reactions, metal redox, conversion and alloying reactions, which can proceed via fast surface- or near-surface-controlled pathways. In other words, greater pseudocapacitive contributions can lead to more efficient lithium storage reactions for MOF-based anode materials.

4.2 Pseudocapacitive contributions in pristine MOFs

Pristine MOF materials are particularly well-suited for pseudocapacitive lithium storage due to their tunable porous architectures, high surface areas, and abundant exposed active redox sites (Morozan and Jaouen, 2012). These structural characteristics facilitate rapid Li⁺ adsorption and charge transfer at the electrode surface, thereby significantly improving rate capability and cycling stability. In pristine MOF anodes, pseudocapacitive behavior enables rapid lithium-ion interaction with the MOF framework and participation in redox reactions involving either the organic ligands or the metal nodes. Consistent with this understanding, numerous experimental studies on pristine MOF anodes have reported dominant or substantial pseudocapacitive contributions, which are widely considered responsible for their excellent rate performance (Dai et al., 2023; Gaber et al., 2024; Li et al., 2025; Liu et al., 2025; Wang et al., 2024; Yin et al., 2020). For example, Dai et al. attributed the enhancement of the capacitive contribution to the abundant active sites and lithium transfer pathways provided by the MOF used in their work, TCPP(Fe)-Ni (Dai et al., 2023), which later showed superior rate capability and high reversible capacity. Interestingly, as shown in Liu et al.’s work, bimetallic nodes in pristine MOFs were found to be capable of promoting the pseudocapacitive contribution, as they compared CoFe-MOF, Co-MOF, and Fe-MOF, whose pseudocapacitive contributions were calculated to be 96.62%, 70.27%, and 39.63%, respectively (Liu et al., 2025).

More importantly, the structure of MOF can be developed or manually tuned such that pseudocapacitive interactions between the lithium ions and the MOF framework can occur more smoothly, thereby boosting the kinetics of lithium storage interactions. A compelling example was provided by Xu et al., who synthesized a Ni-based conductive MOF (Ni-HHTP) on an rGO substrate through an in-situ growth strategy (Xu et al., 2025). Notably, the rGO substrate prevented the MOF from agglomerating, which is ideal for the formation of pseudocapacitance and rapid lithium transport pathways. Although both diffusion and capacitance components controlled the lithium storage at the anode, when the sweep rate increased in the CV measurement, the percentage of the pseudocapacitance also increased to 67% (higher than the 55% capacitance contribution in non-rGO-based Ni-HHTP), which served as the key to an excellent rate capability. Indeed, the anode maintained a reversible capacity of 880 mAh g^-1 even after 500 cycles at 1 A g^-1. Furthermore, the Sn-PMA MOF developed by Xia et al. possessed an intrinsic layered structure, enabling efficient lithium-ion transport and pseudocapacitive reactions within the MOF framework (Xia et al., 2019). As revealed by kinetic analysis, the pseudo-capacitive contribution increased to 85.39% with the rise of the CV scan rate. Benefiting from the fast reaction kinetics, the electrode delivered remarkable rate performance, maintaining a reversible capacity of 707 mAh g^-1 at 800 mA g^-1 after 400 cycles. Beyond intrinsic structures favorable for pseudocapacitive reactions, manually designing and fabricating MOF structures can also help achieve high pseudocapacitive contributions. For example, Zhou et al. fabricated Co-BDCA microspheres with an arcuate petal secondary structure (Zhou et al., 2024). Such a unique hierarchical morphology significantly increased the specific surface area, which was beneficial for surface pseudocapacitive reactions, and exposed a greater number of electrochemically active sites for surface redox. Similar to previous works, the anode contribution to pseudocapacitance increased to 73% with increasing sweep speed, yielding a high rate capability, with the discharge specific capacity remaining at 49.7% when the current was increased to 4 A g^-1. Hence, both intrinsic structural design and external structural engineering of MOFs can effectively enhance pseudocapacitive lithium storage by increasing accessible active sites, shortening ion diffusion pathways, and accelerating surface-controlled redox reactions.

Overall, as a great assistant for ligand intercalation and metal redox reactions, the surface pseudocapacitive behavior provides an effective strategy to accelerate lithium storage kinetics in pristine-MOF-based anodes by enabling fast surface-controlled redox reactions and minimizing diffusion limitations, thereby significantly enhancing rate capability and cycling stability. Moreover, with the extensively exposed active sites not concealed by thick ligand structures or solute molecules, MOF-derived materials are also suitable for pseudocapacitance-facilitated lithium storage in anode applications.

4.3 Pseudocapacitive contributions in MOF-derived materials

Owing to their porous structures, MOF-derived materials are also quite beneficial for pseudocapacitive behavior and the high-rate performance that ensues. Indeed, a number of studies utilizing MOF-derived materials as LIB anodes have demonstrated substantial capacitive contribution (Duan et al., 2023; Gong et al., 2021; Han et al., 2024; Li et al., 2023; Li et al., 2020; Liu et al., 2018; Zheng G. et al., 2021). For instance, Gong et al. have shown that the capacitive contribution in their Co-Mn-O/C electrode impressively rose with the increase in CV scan rate, leading to a promoted high-rate performance of the battery.

Compared to pristine MOF, MOF-derived materials typically exhibit improved electrical conductivity, reduced particle size, and the formation of hierarchical porous structures. These features collectively shorten ion diffusion pathways and facilitate rapid electron transport, thereby favoring surface-controlled charge storage processes. In addition, the derivation process often introduces abundant defects and exposes a higher density of electrochemically active sites, while more advantageous structural features can be developed or designed more freely, which further promotes pseudocapacitive fast redox reactions at or near the surface. For instance, in Li et al.’s work, the rod-like SnO and sphere-like Sn suppressed agglomeration and derived a capacitance contribution as high as 86.87% at a scan rate of 1.0 mV s^-1 (Li et al., 2020). As a result, conventional lithium storage mechanisms, such as conversion reactions or metal redox processes, can increasingly proceed through pseudocapacitive pathways in MOF-derived systems.

Table 4 summarizes the observed pseudocapacitive behavior in the reviewed MOF-based anode studies and their contributions at a specific CV scan rate. Interestingly, MOF-derived materials often exhibit relatively high initial capacitive contributions, whereas pristine MOFs tend to achieve higher capacitive contributions at elevated scan rates. This difference can be attributed to their distinct structural and kinetic characteristics. For MOF-derived materials, the high initial capacitive contribution is mainly associated with their enhanced porosity, nanoscale features, and abundant defects, which promote surface-controlled reactions even at low scan rates. However, due to their relatively limited bulk storage capability and structural disorder, the extent to which diffusion-controlled processes can be further suppressed is restricted, resulting in a smaller increase in capacitive contribution at higher scan rates. In contrast, pristine MOFs typically possess well-defined porous frameworks and more uniformly distributed redox-active sites. At low scan rates, both diffusion-controlled and surface-controlled processes contribute to lithium storage. As the scan rate increases, diffusion processes become increasingly limited, and a larger fraction of charge storage shifts toward surface-controlled pathways, leading to a more pronounced increase in pseudocapacitive contribution.

TABLE 4. Summary of pseudocapacitive contributions in MOF-based anodes at a certain CV scan rate.

From a broader perspective, pseudocapacitive behavior should not be viewed merely as a supplementary effect, but rather as a key design principle for improving lithium storage performance. Through rational structural engineering, such as tuning porosity, unhindered Li⁺ diffusion pathways, and maximizing the exposure of redox-active sites, the pseudocapacitive contribution can be effectively increased.

5 Characterization techniques for identifying lithium storage mechanisms

To better understand lithium storage mechanisms, comprehensive and accurate characterization of the anode materials is essential. In MOF-based lithium-ion battery systems, various experimental and computational techniques have been widely employed to probe structural evolution, redox behavior, and reaction kinetics during cycling. This section reviews commonly used characterization techniques for identifying lithium storage in MOF-based LIB anodes, with representing characterization results summarized in Figure 7.

5.1 Ex Situ XPS and FTIR

Ex situ X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) are powerful techniques for probing reaction-based lithium storage mechanisms in MOF-based anodes. XPS enables the identification of chemical elements in different oxidation states and local chemical environments (Bagus et al., 2018), thereby providing direct evidence of redox processes involving metal centers or other active species. In parallel, FTIR is highly sensitive to changes in chemical bonding and can be used to track the formation and cleavage of specific functional groups during electrochemical reactions (Ţucureanu et al., 2016). In particular, in XPS, shifts in the binding energy of a given element, reflected by changes in peak positions, provide direct evidence of redox processes occurring during charge and discharge. In addition, the integrated peak area, which represents the relative abundance of a specific chemical state, can be used to assess the extent of participation of that element in electrochemical reactions. Complementarily, FTIR spectra offer valuable information on the formation and cleavage of chemical bonds, enabling the identification of structural and chemical changes during lithium storage.

In pristine MOFs, XPS and FTIR can be used to determine whether lithium storage involves ligand-based reactions (e.g., changes in functional groups) or metal-centered redox processes, as well as to characterize reaction intermediates and products. For example, by comparing the XPS spectra of Ni 2p before and after discharge, Zhang et al. discovered no obvious change in peak positions, thus concluding that no reduction of the Ni²⁺ (the metal node of the Ni-tfbdc MOF) occurred during lithiation (Zhang et al., 2023). Meanwhile, the XPS spectra after discharging exhibited peaks for C–C bonds in enol structures and Li–O bonds, leading them to conclude that the redox reaction occurred on the organic ligand, in which Li⁺ was coordinated to the organic moiety. The FTIR spectra after discharging further revealed a change in the ligand state, with a transformation from carbonyl groups to enol structures, as evidenced by the IR peak shift of the C=O bonds. Together, the ex situ XPS and FTIR results indicated that the lithium storage in the Ni-tfbdc MOF was pure ligand intercalation without metal redox involvement (Zhang et al., 2023). In contrast, Li et al. identified a peak change in their Co 2p spectrum after discharging, indicating the reduction of Co³⁺ to Co²⁺, while the appearance of a C–O–Li peak after lithiation indicates a ligand-based reaction. Using FTIR and XPS results, they have preliminarily established the ligand-metal redox interactions in lithium storage in their Co-NTTA MOF anode (Li et al., 2025).

In summary, ex situ XPS and FTIR provide crucial chemical-state evidence for identifying lithium storage mechanisms. Conversely, for MOF-derived materials, XPS and FTIR are less frequently used as a primary tool for mechanistic analysis in MOF-derived materials. Instead, they are often used to compare and analyze chemical compositions (Payam et al., 2024). This is mainly due to the increased structural complexity and heterogeneity introduced during the derivation process, which often leads to overlapping spectral features and ambiguous peak assignments. In addition, since XPS is a surface-sensitive technique, its ability to probe bulk conversion or alloying reactions is inherently limited. As a result, XPS and FTIR are more frequently used in combination with other techniques (e.g., CV or electron microscopy) to provide complementary insights, rather than serving as standalone evidence for lithium storage mechanisms in MOF-derived systems.

5.2 Electron microscopy (SEM/TEM) and EDS analysis

Electron microscopy techniques, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), are primarily used to characterize the morphology and microstructure of MOF-based anodes. While they do not directly reveal lithium storage mechanisms, they provide important supporting evidence by visualizing post-mortem structural evolution during cycling, including volume expansion, particle pulverization, pore formation, and phase transformations. For example, in Baskoro et al.’s study of their MOF anode, the SEM images after charging/discharging cycles revealed a decrease in Pb-BTC porosity and the formation of a new bulk morphology (Baskoro et al., 2021). These structural changes provide indirect evidence of active lithium storage processes occurring within the MOF framework during cycling. TEM can offer insights into lattice changes and amorphization processes, which are often associated with conversion or alloying reactions. Therefore, SEM and TEM are typically used in conjunction with other techniques to correlate structural features with electrochemical performance rather than to independently identify lithium storage mechanisms. Notably, energy-dispersive X-ray spectroscopy (EDS) analysis is often integrated in SEM or TEM, which is more commonly employed as a pre-mortem characterization technique to examine the elemental distribution and compositional uniformity of MOF-based materials. Uniform dispersion of active elements, as revealed by EDS mapping, is particularly important for ensuring sufficient exposure of active sites, as well as homogeneous lithium-ion flux and reaction pathways during electrochemical cycling. For example, in Wang et al.’s work, EDS mapping images demonstrated a uniform distribution of Co, Zn, C, and O elements in the constructed anodes, confirming a successful synthesis with exposed reaction sites (Wang et al., 2024). In the POM-based MOF-derived anodes, quantitative EDS revealed the final ratio of Co₃O₄ and CoMoO₄, showing a successful derivation from the POM-based MOF, while EDS mappings were also employed to show the uniform distribution of active sites (Co, Mo) for conversion reactions (Yang et al., 2020). Such uniform elemental distribution is beneficial for ensuring homogeneous electrochemical reactions and stable lithium storage behavior. In this sense, although EDS does not directly probe lithium storage mechanisms, it provides indirect evidence for the smoothness and reversibility of lithium storage processes by confirming the structural homogeneity of the electrode materials.

5.3 Raman spectroscopy

Raman spectroscopy is able to sensitively identify the vibration spectrum of the analyte, which can be treated as its “fingerprint” (Kudelski, 2008). Owing to such ability, Raman spectroscopy is quite versatile in MOF-based LIB anode research.

Firstly, Raman spectroscopy can be used to confirm the successful synthesis of the anode material by demonstrating the existence of the expected elements. For instance, in Fu et al.’s work, the Raman spectrum of Co₃O₄NPs@MDPC exhibits two prominent peaks located at approximately 473 and 678 cm^-1, which can be assigned to the, E.g., and A1g vibrational modes of Co₃O₄, respectively, confirming the successful formation of crystalline Co₃O₄ nanoparticles (Fu et al., 2018). The confirmed existence of Co₃O₄ lays a foundation for the later conversion-dominated lithium storage. In Jayaramulu et al.’s work, Raman mapping of the Ni–S bond revealed a homogeneous distribution throughout the sample, indicating a uniform conversion from the MOF precursor to nickel sulfide and a well-integrated heterostructure (Jayaramulu et al., 2019). Gao et al. also used Raman spectroscopy to confirm the preserved ligand integrity after the synthesis of ZIF glass (Gao C. et al., 2022). Notably, Raman spectroscopy is particularly useful in carbon-based structures. As shown in Fu et al.’s work, two broad peaks centered at around 1340 cm^-1 and 1590 cm^-1 are observed, corresponding to the D band and G band of carbon. The D band is associated with disordered carbon or defects, while the G band arises from the in-plane vibration of sp²-hybridized carbon atoms. These results indicate that the MOF-derived carbon framework possesses a partially graphitized structure with abundant defects, supporting later results of the carbon matrix providing uniform lithium diffusion pathways and extra lithium storage sites (Fu et al., 2018).

Similar to XPS and FTIR, in MOF-based LIB battery anodes, Raman spectroscopy is widely employed to probe bonding configurations during lithiation in MOF-derived materials beyond structural identification, thus revealing lithium storage mechanisms. For example, in the pristine MOF anode in Ciria-Ramos et al.’s work, operando Raman measurements reveal a gradual red-shift of the aromatic C–C stretching band, indicating a weakening of the π-conjugated system due to Li⁺ insertion and electron transfer to the ligand framework (Ciria-Ramos et al., 2025). More importantly, ex situ Raman analysis reveals distinct evolution behaviors between the breathing mode (associated with the outer regions of the MOF) and the C–C stretching band (related to the internal framework). The breathing mode shows relatively minor changes, whereas the C–C stretching band undergoes more significant shifts after prolonged cycling. This indicates that lithium insertion initially occurs at the MOF boundaries and gradually extends into the inner structure upon cycling (Ciria-Ramos et al., 2025). Finally, ex-situ Raman spectroscopy can demonstrate the stability of the anode structure. In Jayaramulu et al.’s work, ex situ Raman spectra collected after multiple charge-discharge cycles exhibited negligible shifts in peak positions and intensities for both Ni–S vibrations and graphene D/G bands, suggesting excellent structural stability of the composite during lithium insertion and extraction (Jayaramulu et al., 2019). Overall, Raman spectroscopy bridges structural characterization and mechanistic understanding by revealing bonding evolution, spatial lithium storage behavior, and structural stability, thereby providing critical insights into the design of high-performance MOF-based anodes.

5.4 Operando XRD

Beyond ex-situ characterizations like XPS and FTIR, operando characterizations such as operando X-ray diffraction (XRD) can also be used to demonstrate structural and chemical transformations during anode reactions. Operando XRD has been widely employed to directly monitor structural evolution in electrode materials during electrochemical cycling, providing critical insights into battery ion storage mechanisms. Talaie et al. utilized operando XRD to investigate the structural evolution of P2-type Na_0.67 [Mn_0.66Fe_0.20Cu_0.14]O₂ during charge-discharge processes (Talaie et al., 2017). The results revealed multiple phase transitions within the operating voltage window, including transformations from the initial P2 phase to a distorted P′2 phase at low voltage and a low-crystallinity Z-phase at high voltage. These structural changes were accompanied by significant diffraction peak broadening and the loss of long-range order along the c-axis, indicating substantial structural reconstruction rather than simple intercalation behavior. In particular, the emergence of the Z-phase at high voltage was associated with transition metal migration into the interlayer space, reflecting a complex coupling between structural evolution and electrochemical processes. In lithium-ion batteries, Weisenberger et al. utilized operando XRD to monitor the evolution of graphite during cycling and identified distinct phase transitions from graphite to intermediate stages (stage IV/III), followed by LiC₁₂ and ultimately LiC₆, based on characteristic diffraction peaks at ∼26.3°, ∼23.8°, and ∼25.0°, respectively, indicating a typical lithium intercalation mechanism (Weisenberger et al., 2023). Notably, the XRD patterns exhibit well-defined peak shifts and the sequential appearance and disappearance of staging phases, while the overall crystal framework is preserved throughout cycling. In contrast, Lowe et al. employed operando synchrotron XRD to investigate the lithiation of Mn₃O₄ anodes and directly tracked the sequential transformation from Mn₃O₄ to LiMn₃O₄ and subsequently to MnO by identifying highly disordered conversion products (Lowe et al., 2013). Unlike the intercalation case, the XRD patterns show the gradual disappearance of the original diffraction peaks, sudden emergence of new diffraction peaks, and the formation of highly disordered products, reflecting a complete structural reconstruction associated with conversion reactions. These distinct diffraction features highlight the capability of operando XRD to differentiate lithium storage mechanisms: intercalation processes are characterized by reversible peak shifts and staged phase evolution within an intact framework, whereas conversion reactions involve phase decomposition, the formation of new phases, and loss of long-range crystallinity. Although these works did not study MOF-based lithium battery anodes, operando XRD has still been proven to be useful for lithium storage research.

Operando X-ray diffraction is not only useful for identifying phase transitions, but also serves as a powerful tool to evaluate structural stability and degradation mechanisms under realistic operating conditions. For example, Sheng et al. employed operando XRD to investigate the structural evolution of Ni-rich NMC622 cathodes in electrolytes containing high levels of water impurities (Sheng et al., 2023). The results showed that the (003) diffraction peak exhibited a significantly smaller shift in cells using MOF-modified separators compared to conventional polypropylene separators, indicating reduced lattice expansion and enhanced structural reversibility during cycling.

In summary, operando XRD is potential to be useful in identifying lithium storage strategies in MOF-based lithium battery anode materials, but limited studies have employed such a technique. Therefore, in the future study of MOF-based lithium anodes, operando XRD should be actively applied to reveal lithium storage mechanisms.

5.5 Electrochemical analysis

5.5.1 Cyclic voltammetry (CV)

Cyclic voltammetry (CV) is one of the most widely used electrochemical techniques for probing lithium storage mechanisms and reaction kinetics in MOF-based anodes. By analyzing the shape of CV curves, the position of redox peaks, and their evolution with scan rate, valuable insights into both thermodynamic and kinetic processes can be obtained (Mathis et al., 2019; Pu et al., 2021). In particular, the presence and position of the redox peaks reflect the occurrence of Faradaic reactions and can be used to identify the types of electrochemical processes involved, such as intercalation, conversion, or alloying reactions. The evolution of peak positions and peak separation during cycling further indicates the reversibility of these reactions and the degree of polarization within the electrode. Additionally, the shape of the CV curve provides qualitative information on whether diffusion or capacitive interactions are dominant in storing lithium, as well-defined redox peaks are typically associated with diffusion-controlled battery-type processes, whereas quasi-rectangular CV profiles suggest that capacitive or pseudocapacitive behavior, dominated by fast surface-controlled reactions, is dominant. The relationship between current and scan rate can be used to distinguish between diffusion-limited and surface-controlled processes, as mentioned in previous sections, while the relative contribution of pseudocapacitance can be evaluated through current decomposition methods. Finally, changes in CV profiles across repeated cycles can be used to assess structural stability and reaction evolution during lithium storage, including activation processes, irreversible reactions, and the formation of solid electrolyte interphase (SEI) layers.

Gaber et al.’s work provides a compelling example of the use of CV analysis for pristine MOF anodes (Gaber et al., 2024). During their CV scan, they identified two sharp, distinctive redox peaks, indicating stable, reversible lithiation and delithiation via redox reactions. Furthermore, they also noticed that the capacitive contribution arose with an increase in the scan rate. Baskoro et al. discovered reversible conversions between Pb⁴⁺ and Pb²⁺, and between Pb²⁺ and Pb⁰, by analyzing the CV peaks, which not only confirmed the metal node redox mechanism but also indicated the reduction of the high Pb oxidative state rather than merely Pb²⁺ (Baskoro et al., 2021). CV analysis has also been widely used to identify complex lithium storage mechanisms involving multiple reaction pathways in MOF-derived materials. In the case of Mn₂SnO₄/C anodes, the appearance of a cathodic peak around 0.45 V during CV scan was associated with reversible alloying reactions of Sn with Li and the conversion reactions involving Mn and Li₂O (Duan et al., 2023). The evolution and stabilization of these peaks, together with the overlap of CV curves in subsequent cycles, suggest good reversibility and the coexistence of alloying and conversion mechanisms during lithium storage. Also, a pronounced cathodic peak at around 0.31 V in the first cycle was attributed to the irreversible decomposition of Mn₂SnO₄ and the formation of the solid electrolyte interphase (SEI). This peak disappeared in subsequent cycles, indicating the irreversibility of the initial activation process. Then, by altering the CV sweep rate, the researchers found minimal anode polarization and observed an increase in capacitive contribution with increasing scan rate.

Overall, CV serves as a versatile and powerful tool for characterizing lithium storage mechanisms and kinetics in both pristine MOF and MOF-derived anodes, enabling the identification of reaction pathways, evaluation of reversibility, and quantification of pseudocapacitive behavior.

5.5.2 EIS analysis

Electrochemical impedance spectroscopy (EIS) is an important technique for evaluating the kinetics of lithium storage processes in MOF-based anodes. Although it does not directly identify the specific lithium storage mechanism, EIS provides valuable information on charge transfer resistance, ion diffusion, and interfacial properties. Typically, a smaller charge-transfer resistance (R _ct) indicates faster electrochemical reactions, whereas the Warburg impedance at low frequencies reflects lithium-ion diffusion within the electrode material (Qu et al., 2022). A deviation of the low-frequency straight line from 45° is often associated with increased pseudocapacitive contributions or improved ion transport (Yin et al., 2020). In addition, features at high frequencies are often associated with the formation and stability of the solid electrolyte interphase (SEI). Therefore, EIS serves as a complementary tool to CV and spectroscopic techniques for understanding lithium storage behavior. For instance, the EIS diagram in Hu et al.’s work revealed a relatively small charge-transfer resistance without substantial change over cycling, indicating a rapid solid-state Li⁺ diffusion rate and limited SEI layer growth (Hu et al., 2016). Similarly, Zheng et al. uncovered a smaller charge-transfer resistance in the CoS₂-MnS@rGO MOF-derived anode (160 Ω) than uncomposited materials, proving better Li ion transfer during storage reactions (Zheng J. et al., 2021).

5.5.3 GITT

Galvanostatic intermittent titration technique (GITT) is an effective electrochemical method to evaluate the Li⁺ diffusion kinetics in electrode materials. By applying a series of current pulses followed by relaxation periods, GITT enables the determination of the chemical diffusion coefficient (D _Li ⁺) at different states of charge (Zhu and Wang, 2010).

The most common usage of GITT in MOF-based LIB anodes is therefore to evaluate lithium diffusion behavior during lithium storage, thereby providing insights into structural design and storage mechanisms. For instance, Lv et al. investigated the lithium storage behavior of MOF-derived CoFe₂O₄/FeO/Fe nanocomposites using GITT measurements (Lv et al., 2022). The calculated Li⁺ diffusion coefficients of the optimized Fe-Co-700 sample were significantly higher than those of the other samples, which was attributed to the nanoscale particle size, abundant active sites, and structural defects introduced by the multi-phase composite structure, all of which effectively shortened the lithium diffusion pathways and facilitated the conversion reaction for storing lithium.

GITT is also able to identify conversion-based lithium storage when being conducted under different potentials. Park et al.’s work, despite the usage of a non-MOF-based anode, demonstrated that the formation of a new lithium-containing phase can result in a decrease in diffusion coefficient yielded by GITT (Park et al., 2021). In MOF-based anodes, the measured change in diffusion coefficient therefore indicates a newly formed lithium phase, thereby offering information on lithium storage mechanism. For instance, in the pristine Ni-MOF anode developed by Guo et al., GITT not only confirmed promoted Li⁺ transportation but also indicated formation of a new Li-ligand phase as the diffusion coefficient decreased with an increase in potential, supporting the ligand intercalation lithium storage (Guo et al., 2019). In Lv et al.’s work, the Li⁺ diffusion coefficient obtained from GITT exhibits pronounced variation with potential, with local minima appearing near redox plateaus (Lv et al., 2022). These features indicate the presence of phase transformation processes associated with conversion reactions, where lithium insertion leads to the formation of new phases (e.g., Li₂O and metallic species), thus temporarily hindering Li⁺ transport.

Therefore, GITT analysis in MOF-based anode systems not only confirms fast lithium diffusion but also indirectly supports ligand-based intercalation or conversion-dominated lithium storage mechanisms.

5.6 Density functional theory (DFT)

Density functional theory (DFT) calculations have been widely employed to provide theoretical insights into lithium storage mechanisms in MOF-based anodes (Sun et al., 2025). Unlike experimental techniques, DFT enables atomic-scale understanding of lithium-ion interactions with the electrode material, including adsorption behavior, diffusion pathways, and electronic structure. DFT calculations can be used to evaluate the adsorption energy of lithium ions at different active sites (Zhao et al., 2021), thereby identifying the preferred lithium storage locations, such as metal nodes, organic ligands, or defect sites. In addition, the calculation of diffusion energy barriers provides important information on lithium-ion transport kinetics within the material. Electronic structure analysis, including density of states (DOS), further helps to explain conductivity and redox activity. In many studies involving MOF-based anodes, DFT calculations are employed as essential theoretical support for lithium storage mechanisms inferred from other experimental characterizations, such as XPS, FTIR, and CV curves.

For example, Li et al. employed DFT calculations to elucidate the lithium storage mechanism in their Co-NTTA MOF, with a particular focus on the role of aromatic ligands in lithium-ion uptake (Li et al., 2025). Through electrostatic potential (ESP) analysis, they identified that oxygen-containing functional groups (C=O) possess more negative potential and thus serve as the initial preferred lithiation sites. As lithiation proceeds, additional Li⁺ ions interact with other functional groups and eventually bind to selectively activated inner aromatic rings. Moreover, DFT results showed that Li⁺ binding to aromatic rings is weaker than to oxygen-containing functional groups, facilitating faster adsorption/desorption kinetics and contributing to pseudocapacitive behavior. Similarly, in Gaber et al.’s study of MOF-derived anode materials, the superior lithium storage performance of the MOFite anode was attributed to the presence of abundant lithiophilic sites and extended π-d conjugation within the framework (Gaber et al., 2024). Although detailed DFT analysis was not the central focus, the design concept aligns with theoretical insights that electron-rich conjugated structures and high-density active sites can enhance Li⁺ adsorption and facilitate rapid charge transfer, thus promoting efficient lithium storage. These studies highlight that DFT not only identifies lithium storage sites but also reveals how local chemical environments and electronic structures govern lithium storage pathways and kinetics.

Table 5 summarizes the reviewed characterization techniques commonly used to study the lithium storage mechanisms of MOF-based LIB anodes as well as their functions.

TABLE 5. Reviewed characterization techniques for lithium storage mechanism studies.

6 Conclusion and future perspectives

6.1 Overall conclusion

A comprehensive overview of lithium storage mechanisms in MOF-based anodes in this review, including pristine MOFs and MOF-derived materials, with a particular focus on their reaction pathways and kinetic behaviors. In pristine MOFs, lithium storage typically involves ligand-based redox, metal-centered redox, or their synergistic interactions, enabled by well-defined coordination environments and tunable organic-inorganic frameworks. In contrast, MOF-derived materials often exhibit conversion and alloying reactions arising from structural transformations into more complex, heterogeneous phases. By summarizing all lithium storage mechanisms, it should be noted that, for pristine MOFs, the combination of multiple redox centers, such as bimetallic redox and ligand functional group redox, can help achieve higher battery performance. In MOF-derived materials, it is of great significance to composite the derived metal compounds with carbon matrices, which can not only facilitate electron and ion transfer, thus laying a steady foundation for alloying reactions ensuing conversion reactions, but also suppressing catastrophic structural alterations during lithiation and delithiation, thereby inducing better cycling stability of the battery.

Beyond classifying lithium storage mechanisms, this work highlights the critical role of pseudocapacitive behavior in enhancing lithium storage kinetics. Rather than representing an independent storage mechanism, pseudocapacitance reflects a surface-controlled contribution that coexists with diffusion-limited processes, effectively bridging battery-type and capacitive behaviors. The analysis of CV kinetics demonstrates that increasing scan rate shifts the storage contribution toward pseudocapacitive dominance, thereby improving rate capability. Interestingly, while MOF-derived materials often exhibit higher initial capacitive contributions due to their abundant exposed active sites and porous structures, pristine MOFs may achieve higher pseudocapacitive fractions at elevated scan rates, owing to their more ordered frameworks and well-defined redox centers that facilitate reversible surface-controlled reactions. It has also been noticed that intentionally developed reasonable pristine MOF structures, such as layered or flower-like morphologies, are able to promote pseudocapacitive contributions, while constructing hierarchically porous structures for MOF-derived materials based on their intrinsic porosity and small particle sizes is also quite useful for enhancing pseudocapacitive behaviors.

Furthermore, the importance of combining multiple characterization techniques to identify lithium storage mechanisms accurately is emphasized. Electrochemical methods such as cyclic voltammetry and impedance spectroscopy provide insights into reaction kinetics and capacitive contributions, whereas GITT can be used to investigate lithium diffusion and identifying phase change during Li intercalation and conversion. In contrast, spectroscopic techniques such as XPS,FTIR and Raman spectroscopy reveal redox-active species and chemical transformations, while SEM/TEM plus EDS are able to reveal anode structural evolution and element mapping. Structural characterization and theoretical calculations, including operando XRD and DFT, further complement experimental observations by elucidating phase evolution and atomic-scale interactions. The integration of these approaches is essential for achieving a holistic understanding of lithium storage behavior.

6.2 Future research directions

Future research on MOF-based LIB anodes should continue to focus on the rational design of multi-redox-active pristine MOFs and composite MOF-derived materials. In particular, future material design for MOF-based LIB anodes can be broadly categorized into three key aspects: (i) multi-redox activity, (ii) extra storage sites, and (iii) sustainable development. Figure 8 provides a predictive framework for future MOF-based anode designs.

6.2.1 Multi-redox activity

Promoting multi-redox activity in LIB anodes is considered to be a promising direction because of the excessive electron transfer it brings. For both pristine MOF and MOF-derived materials, constructing anode materials that integrate multi-metallic redox or conversion reactions (involving more than two metal centers) should be further researched. In particular, incorporating elements capable of accessing higher oxidation states can enable greater electron transfer during conversion reactions, thus contributing to higher capacity and improved energy density.

6.2.2 Extra storage sites

For pristine MOFs, the inherent chemical tunability of the framework enables the deliberate incorporation of functional groups that provide abundant Li⁺ storage sites and redox-active centers, thereby enhancing capacity and reaction kinetics. For example, benzene rings that are in various chemical environments can be introduced to increase the lithium storage capacity and provide additional cation-π interaction sites. For MOF-derived materials, optimizing hierarchical structures (adjusting the ratio of mesopores and micropores) and conductive networks is predicted to be critical for facilitating charge transfer, especially for alloying reactions and carbon-based surface storage, as such rationally designed architectures accelerate Li⁺ diffusion and maximize the utilization of available active sites. This can be achieved by investigating different synthesis conditions of MOF-derived materials and various doping strategies on derived carbon frameworks. It is also expected to promote pseudocapacitive contributions and maintain structural stability during cycling.

6.2.3 Sustainable development

In addition to performance optimization, sustainability considerations should be increasingly emphasized. To ensure sustainable and practical applications, the integration of toxic organic ligands or hazardous metal nodes in MOF architectures should be strictly avoided, while green synthesis strategies for MOF-based materials, such as using industrial wastes or low-cost precursors, together with the selection of environmentally benign and non-toxic elements, are highly desirable for large-scale applications. Environmentally friendly organic compounds can be sought for future MOF anode design. For MOF materials containing toxic elements, such as Pb-based MOFs, safe synthesis procedures and waste processing should be actively sought in order to minimize the risk to which the researcher’s health and the environment are exposed.

Overall, future efforts should focus on advanced material design, including multi-redox activity, extra lithium storage sites, and sustainable synthesis approaches to enable the development of MOF-based LIB anodes with high capacity, superior rate capability, long-term cycling stability, and reduced environmental impact. Increasing the number of redox-active centers or introducing multimetallic nodes is expected to enhance conversion capacity, while hierarchical porosity and conductive networks are more likely to promote pseudocapacitive behavior and improve rate performance. Establishing a clear correlation between structural design and lithium storage mechanisms will be essential for enabling the predictive design of next-generation MOF-based anodes as well as higher-quality lithium batteries.

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Footnotes

Edited by: Xingcheng Xiao, General Motors, United States

Reviewed by: Panpan Dong, Southwest Jiaotong University, China

Gaurav Tatrari, Luleå University of Technology, Sweden