Lithium-ion batteries(LIBs),as the most widely studied energy storage system in the secondary battery system,have a higher working voltage,which is three times that of nickel-hydrogen batteries,usually greater than 3.6 V,and a higher power density.It has been widely used in the market of power batteries,energy storage batteries and portable electronic devices^[23]。 In recent years,the theoretical capacity and specific energy density of traditional lithium-ion batteries with lithium cobalt oxide and lithium iron phosphate as the cathode and graphite as the anode have reached the upper limit,which hinders the further development of lithium-ion batteries.Therefore,researchers have tried to improve the capacity and rate performance of lithium-ion batteries by preparing MOFs-related materials instead of traditional electrode materials。

the porous structure of MOFs can enhance the contact area between the active material and the electrolyte,which is conducive to the improvement of the rate performance of lithium-ion batteries and the rapid diffusion of lithium ions,so it shows great potential as an electrode material for lithium-ion batteries^[12]。 Lin et al.Used a solvothermal method to synthesize a Cd-MOF with excellent thermal stability and further calcined it at 800°C under nitrogen protection to obtain a nitrogen-doped carbon material NC800,which was tested to have excellent cycling stability(after 100 cycles at a current density of 100 mA·g^-1,the specific capacity remained at 741 mAh·g^-1）^[24]。 Recently,the multi-metal doping modification of MOFs has been widely studied as anode materials for lithium-ion batteries.The construction of bimetallic MOFs can enhance their electrochemical performance,because the multi-component metal nodes can expose more reactive sites,and the obvious advantages of kinetics and thermodynamics can constitute a synergistic effect.Yan et al.Constructed a bimetallic Co₄(μ₄-O)[Ir(ppy-COO)₃]₂MOF（Co₄-Ir MOF）as an anode material for lithium-ion batteries.Such bimetallic MOFs composed of Ir(ppy-COOH)₃bridging-coordinated Co₄(μ₄-O)clusters(Figure 1A)have 4 orders of magnitude higher electrical conductivity and 2 orders of magnitude higher Li-ion diffusion coefficient than conventional insulating MOFs,reaching a good rate capability of 515 mAh·g^-1at 3000 mA·g^-1[25][26]。 Multi-metal materials are used as precursors to further prepare metal selenides.The higher polarization of selenium can theoretically bring better rate performance,while nitrogen-doped carbon can improve conductivity.Zhang et al.Proposed a KOH-assisted aqueous strategy to synthesize a series of bimetallic MOFs materials,which were further carbonized and selenized to obtain 3D polyhedral Fe-Co-Se/NC with intact porous structure.As a lithium-ion anode,the initial discharge specific capacity was up to 1165.9 mAh·g^-1at a current density of 1.0 A·g^-1,and the reversible capacity was 1247.4 mAh·g^-1（after 550 cycles(Fig.1D )^[27]。

Recently,Dai et al.Synthesized bimetallic MOFs material TCPP(Fe)-Ni by solvothermal method,which showed excellent rate performance and high reversible capacity of 950 mAh·g^-1at 0.1 A·g^-1when used as anode material for lithium-ion batteries^[28]。 Yin et al.Proposed a simple one-step method to synthesize two-dimensional c-MOF Cu₃(HHTP)(THQ)based on two ligands,in which ethylenediamine was used to balance the competitive coordination between HHTP and THQ ligands,which opened up a new way for the synthesis of two-dimensional c-MOF with two ligands^[29]。

MOFs and their derivatives are considered to be excellent candidates for electrode materials for lithium-ion batteries.In order to effectively improve the electrochemical performance,the strategies of doping multi-metal components and preparing metal matrix composites are proposed,which help us further explore the application of MOFs derivatives as anode materials for lithium-ion batteries。

sodium is abundant in natural resources and cheaper,and its electrochemical mechanism is similar to that of lithium-ion batteries,so it is expected to replace lithium-ion batteries in large-scale energy storage applications.However,sodium has a larger ionic radius than lithium(102 pm vs.76 pm),resulting in slow kinetics of the electrode material during sodium intercalation/deintercalation cycles and large structural changes in the matrix material.Therefore,electrode materials with good structural stability should be developed to achieve improved electrochemical performance of sodium-ion batteries(SIBs)^[30]。

in order to improve the sodium storage performance,carbon materials(including graphite,amorphous carbon,heteroatom-doped carbon and biomass-derived carbon)have been widely studied In recent years.Based on this idea,carbon materials derived from MOFs may become high-performance anode materials for sodium-ion batteries because they not only retain the original high pore structure but also enhance the conductivity^[31]。 Cui et al.Proposed that heteroatom doping in porous carbon materials improves the sodium storage performance^[32]。 Based on the concept of excellent sodium storage for heteroatom-doped carbon materials and metal phosphides,recently,Zhao et al.Mixed ZIF-67 and red phosphorus,and further calcined in a protective atmosphere to obtain nitrogen-doped cobalt phosphide carbon composite Co₂P@NC-12.5（Fig.2a),which showed a reversible capacity of more than 350 mAh·g^-1at a current density of 0.1 A·g^-1when used as an anode material for sodium-ion batteries^[33]。 Feng et al.Prepared the CoSe@NC/MoSe₂bimetallic selenide composite(Figure 2D)by combining the ideas of metal selenide,nitrogen doping,and carbon skeleton to prepare the composite^[34]。 This multi-component composite strategy improves the sodium storage performance,while the nitrogen-doped carbon matrix ensures the sodium ion transport capacity.After 1500 cycles at a current density of 5.0 A·g^-1as a sodium ion anode material,the discharge capacity was 305.9 mAh·g^-1（Fig.2 e).Li et al.Grown a new carbon allotrope,graphite-like crystal,under sufficient graphite induction conditions,and successfully prepared Zn-TDPAT MOF-derived crystalline carbon by controlling the reaction inflection point temperature under graphite induction(Fig.2F).The Zn-TDPAT-GC electrode showed excellent electrochemical performance and good structural stability when applied to sodium ion anode.The reversible capacity was 354 mAh·g^-1after 50 cycles at a current density of 20 mA·g^-1,which was 97.5%of the initial capacity,and 293 mAh·g^-1after 100 cycles at a current density of 100 mA·g^-1,which was 90%of the initial capacity(Fig.2 H )^[35]。

Recently,the ideas of defect introduction and heteroatom doping have been widely used in the research of improving the performance of electrode materials for sodium-ion batteries.Yao et al.Doped in MIL-125 by solvothermal method,and then further prepared Si-TiO_2-x@C materials with Si atom doping and oxygen vacancy defects by annealing and NaOH etching.The existence of oxygen vacancy defects was verified by EPR,which enhanced the conductivity and reaction kinetics.When the Si-TiO_2-x@C materials were used as sodium ion anode materials,they showed excellent performance^[36]。 Feng et al.Prepared MIL-101(Al)-NH₂MOF as a precursor,and then mixed with sulfur and calcined to obtain a nitrogen/sulfur binary doped microporous carbon material NSPC as an anode material for sodium-ion batteries.The initial coulombic efficiency(ICE)was improved due to the coating effect of sulfur in the micropores,which reduced the internal defects of the micropores^[37]。 the adsorption energy of sodium ions on the surface of nitrogen/sulfur co-doped carbon materials was significantly increased(-0.5 eV to-2.07 eV)compared with that of nitrogen doped carbon materials,which proved that the synergistic effect of double heteroatom doping increased the diffusion rate of sodium ions。

MOFs-derived carbon materials,Metal compounds And multi-component doped composites combine their respective advantages and show excellent electrochemical performance in sodium-ion batteries.metal compounds improve the performance of sodium storage,and heteroatom doping(Si,N,S,etc.)and defect regulation effectively enhance the reaction kinetics.These modification design strategies contribute to the rapid development of MOFs as anode materials for sodium-ion batteries。

potassium resources on the earth are more abundant than lithium resources,and the conductivity of Potassium electrolyte is better,and the voltage platform and energy density are higher^[38]。 the similar working mechanism of lithium-ion batteries makes potassium-ion batteries(PIBs)promising as one of the alternatives to lithium-ion batteries.the radius of potassium ion(138 pm)is larger than that of lithium ion and sodium ion,which leads to the fact that many electrode materials suitable for lithium ion batteries can not be directly applied to potassium ion batteries.It will lead to huge volume expansion and serious capacity fading in the process of potassium intercalation/deintercalation,so finding anode materials that can reversibly accommodate potassium ions is the key to promote the development of potassium-ion batteries^[39]。

In order to solve the problems of low capacity and poor cycle performance of electrode materials,Xiao et al.Grew Co-MOF nanocrystals uniformly anchored on graphene oxide through the synergistic coordination and electrostatic interaction between GO and Co-MOF,and further annealed to obtain a hybrid material composed of Co-MOF nanocrystals tightly coated with reduced graphene oxide(rGO)network(Figure 3A)^[40]。 When the prepared three-dimensional graphene-network-encapsulated Co-MOF nanocrystals(Co-MOF-rGO)was used as the PIB anode material,it showed a reversible specific capacity of 422 mAh·g^-1at 0.1 A·g^-1,and the discharge specific capacity could still reach 202 mAh·g^-1even at a large current density of 5 A·g^-1,demonstrating the excellent rate capability of Co-MOF-rGO,with a decay rate of only 0.013%per cycle after 2000 cycles at 2 A g^-1(Fig.3 B).In recent years,bismuth-based MOFs have been widely used as anode materials for potassium-ion batteries.Bismuth is non-toxic and environmentally friendly,with a theoretical mass specific capacity of（386 mAh·g^-1）and a high volume specific capacity(3800 mAh·L^-1）.The coordination of Bi metal center with potassium ion can increase the reversible ability,but there are also problems of volume expansion(PIBs about 411%)and electrode pulverization inherent to bismuth metal as a negative electrode^[41]。 Based on this idea,Sun et al.Synthesized a novel flower-like Bi-MOF assembled by two-dimensional porous nanosheets by solvothermal method,and further calcined Bi@N-CNCs with melamine as nitrogen source in Ar atmosphere(Fig.3C).When the further optimized 850Bi@N-CNCs were used as anode materials for potassium-ion batteries,the reversible capacities were 334.3 and 221.3 mAh·g^-1at a current density of 0.5 and 10.0 A·g^-1,respectively,and the capacity fading rate was only 0.004%per cycle after 1200 cycles at 5.0 A·g^-1[42]。 Recently,Li et al.prepared a 3D-structured Bi-MOF(Figure 3D)as a potassium ion anode material through metal bismuth and terephthalic acid.the three-dimensional porous structure of the nanoscale pore disperses the stress generated by the alloy reaction,effectively suppresses the volume expansion problem,and thus promotes the ion transport capability^[39]。 When used as an anode material for PIB,the Bi-MOF delivered a high reversible capacity of 415 mAh·g^-1after 500 cycles at 0.1 A·g^-1and excellent cycling stability(315 mAh·g^-1）at 0.5 A·g^-1at 1200 cycles.Selenides have also been used in combination with porous carbon materials for potassium storage applications.Chen et al.Synthesized Bi-MOF by hydrothermal method,and after further pyrolytic selenization under Ar atmosphere,synthesized Bi/Bi₃Se₄@CNR composite composed of rod-like porous carbon skeleton in the outer layer and Bi/Bi₃Se₄nanoparticles in the inner layer(Fig.3e),and in situ characterization proved that the potassiation/depotassiation process was controlled by the dual mechanisms of conversion and alloying/dealloying reactions^[43]。 The battery can exhibit a good reversible capacity of 307.5 mAh·g^-1at 20 A·g^-1.After 2000 cycles at 5 A·g^-1,the capacity reached 254.8 mAh·g^-1.In addition,Bi/Bi₃Se₄@CNR/KVO full batteries also show some application potential 。

MOFs composites prepared by adding carbon-based materials such as graphene and graphene oxide have effectively improved the electrochemical performance of anode materials for potassium-ion batteries,and two-dimensional and three-dimensional structures and metal selenides have also shown great potential in anode materials for potassium-ion batteries in recent years。

the negative electrode of the battery is made of alkali metal,and the positive electrode is made of chalcogenide.This kind of alkali-chalcogenide battery has become a hot topic in the field of energy storage batteries because of its low cost,large theoretical capacity,green environmental protection and other characteristics^[17]。 For example,lithium-sulfur batteries include a lithium metal negative electrode,an organic electrolyte,and a sulfur composite positive electrode.In the research of this kind of battery,MOFs materials can be used as active materials to suppress the volume expansion of the electrode during charge and discharge.the modified separator and protective coating prepared by MOFs can also solve the shuttle effect caused by the intermediate entering the electrolyte and the dendrite growth caused by the alkali metal electrode。

in order to effectively limit the shuttle effect of polysulfides(long-chain polychalcogenides produced by the positive electrode of alkali-metal chalcogenide batteries can dissolve in common ether electrolytes and react with the negative electrode through the separator,resulting in irreversible losses),Zheng et al.It is found that the interaction between Lewis acidic Ni(II)centers and Lewis basicity of polysulfides can successfully capture polysulfides in the framework of MOFs and enhance their cycle stability.This confirmation of polysulfide absorption based on Lewis acid-base theory helps to improve the design of such battery materials^[44][45]。 Bai et al.Designed and prepared a microporous MOF@GO separator for lithium-sulfur batteries(Figure 4A),which has regular pores of about 99Å,effectively blocking the passage of polysulfides and allowing the normal movement of lithium ions^[46]。 Based on the previous idea of MOFs separator preparation,Li et al.Recently developed a functional separator for lithium-sulfur battery ZIF-67 in-situ growth of sodium alginate fiber membrane by electrospinning(Fig.4B).As a new multifunctional lithium-sulfur battery separator(ZIF-67/SA-PAN),the SA fiber membrane prepared by in-situ loading ZIF-67 on polyacrylonitrile(PAN)matrix can effectively isolate polysulfides(Figure 4C),and shows good rate performance and cycle stability in further tests^[47]。 Geng et Al.Prepared MIL-96-Al with different shapes and sizes,and analyzed the effects of shape and size on its electrochemical performance,which provided an improvement idea for the size design of MOFs materials^[48]。

in the aspect of limiting the dendrite growth of alkali metal anode in lithium-sulfur battery,Song et al.Prepared Bio-MOF-100,and then carbonized it at 800℃for 8 H in Ar atmosphere to obtain amorphous carbon material ZnENC^[49]。 SAZ-AF Janus membrane was prepared by coating Bio-MOF-100 and ZnENC on both sides of Celgard membrane.The Bio-MOF-100 coating layer toward the lithium anode side separator effectively induced uniform and fast transport of lithium ions(Figure 4D),which can suppress dendrite growth even at high current densities.The introduction of additional metal nodes into MOFs materials can effectively optimize the application of MOFs materials in lithium-sulfur batteries.This is due to the fact that MOFs materials with bimetallic and multimetallic nodes can enhance the absorption of polysulfides in lithium-sulfur batteries.Recently,Zhu et al.Proposed to encapsulate Ni-Co bimetallic phosphide into a nitrogen-doped double carbon conductive network(NiCoP@NC)by high temperature annealing and phosphating Ni-ZIF-67 precursor(Fig.4E),and the encapsulated Ni/Co phosphide particles can significantly enhance the catalytic conversion of lithium polysulfides.As a modified separator for lithium-sulfur batteries,it helps lithium-sulfur batteries to exhibit good specific capacity(the initial capacity at 0.5 C is 1083.4 mAh·g^-1）)and good cycle stability(the capacity fading rate is only 0.09%at 300 cycles )^[50]。 For the synthesis of multi-metal doping,the one-pot synthesis method can be used,and the ion exchange method can also be used by soaking the monometallic MOFs in different concentrations of metal ion solution^[51]。 Li et al.Prepared a series of Mn-based multimetallic MOFs(bimetallic and trimetallic MIL-100)nanooctahedra(Figure 4 f)through a one-pot synthesis strategy,which were used as sulfur carriers for lithium-sulfur battery cathodes,and the MnNiMIL-100@S cathode showed the best lithium-sulfur battery performance after testing,with a reversible capacity of about 708.8 mAh·g^-1after 200 cycles^[52]。

Modified separators based on MOFs and their derivatives can effectively adsorb polysulfides when applied to metal-chalcogenide batteries.A separation membrane(Janus separator)with an asymmetric structure can be prepare as a coating layer to induce uniform deposition of a lithium anode to a certain extent.In addition,the cathode sulfur support materials prepared by multimetallic MOFs also show good electrochemical performance。

Compared with non-aqueous system,aqueous zinc-ion battery has higher safety and lower cost,so it has been widely concerned by researchers.Manganese-based and vanadium-based oxides,Prussian blue analogues,and metal salts of the Prussian blue type have been studied as cathode materials for aqueous zinc-ion batteries^[53]。 However,due to the low specific capacity of cathode materials and the dendritic growth of anode zinc metal(caused by uneven zinc deposition),the further development of aqueous zinc-ion batteries is still seriously hindered^[54]。 In order to improve the above problems of aqueous zinc-ion batteries(ARZIBs,ZMB),researchers have done a lot of work on the application of MOFs materials as cathode materials,anode materials,separators and solid electrolytes^[18]。

In terms of alleviating the dendrite growth of zinc anode,MOFs materials are often used to prepare ion sieves due to their structural characteristics,but the prepared ion sieves are still vulnerable to severe polarization and dendrite growth after multiple cycles on ZMB^[55]。 Lei et al.Experimentally demonstrated that two-dimensional MOFs nanosheets(Figure 5A)can act as a protective coating to inhibit dendrite formation^[56]。 In addition,the researchers compared the differences between UiO-67-3D and UiO-67-2D materials as zinc anode coatings,and verified that the two-dimensional structure has a higher concentration of Zr-OH/H₂O zincphilic sites,which can induce the uniform deposition of Zn and better inhibit the growth of zinc dendrites.The UiO-67-2D@Zn||Mn₂O₃/C battery tested by this coating also achieved good reversible capacity,rate performance and cycle stability.Yang et al.Proposed to use MOFs coating on Zn surface for high-performance MnO₂-Zn batteries,and the construction of MOFs coating layer to obtain uniform Zn deposition and then prevent the dendrite growth of zinc anode(Fig.5B )^[57]。 The symmetrical Zn half cell was maintained for a lifetime of up to 3000 H at a current density of 0.5 mA·cm^-2.When complexed with MnO₂cathode,the reversible capacity was 180.3 mAh·g^-1with a capacity retention of 88.9%after 600 cycles at a MnO₂loading up to 4.2 mg·cm^-2.Similarly,UiO series MOFs were designed to solve the problem of zinc anode dendrite growth.Xu et al.Prepared a UiO-66 defect layer(Figure 5C),and further prepared a defect MOF(D-UiO-66)on the zinc surface,and then used the quasi-solid interface phase composed of it and two zinc salt electrolytes as the zinc ion reservoir^[58]。 By verifying the anion adsorption and zinc ion transfer efficiency of Lewis acid sites in the defect layer of MOFs,the concentration of zinc ions near the anode is increased,which further proves that it can inhibit the dendrite growth of zinc。

Because the regulation of intrinsic structure is an effective modification strategy to enhance electrochemical performance,researchers found that the steric hindrance of lattice space can hinder the efficiency of zinc ion transport.To this end,Ren et al.Used amorphous metal-organic framework materials(aMOFs)synthesized by Zr⁴⁺and ATMP one-step solvothermal method to prepare artificial SEI films,which achieved better zinc ion transport and uniform deposition according to their defects and dangling bonds and microporous structure different from crystalline MOFs,which also opened the way for aMOFs to be applied to aqueous zinc-ion batteries^[59]。 In addition,Yin et al.Made cathode materials through the idea of coordination unsaturation,in which three Mn-based MOFs with different coordination degrees were synthesized by adjusting the molar ratio of Mn to H₃BTC during the preparation process(Fig.5d)(in which the molar ratio of Mn to-COOH was 1:Subsequent tests verified that Mn-H₃BTC-MOF-4 at a molar ratio of 1:4 possessed a better zinc ion storage capacity than several other coordination degrees(excellent capacity of 138 mAh·g^-1at 100 mA·g^-1and 93.5%capacity retention after 1500 cycles at 3000 mA·g^-1)(Fig.5e )^[60]。 Recently,based on 2D-MOF materials,Wang et al.Proposed an alternative stacked Cu-HHTP/MX heterostructure prepared by solution phase direct assembly strategy for aqueous zinc-ion battery cathode materials(Figure 5F),which was tested to have a capacity of 260.1 mAh·g^-1at a current density of 0.1 A·g^-1,a rate capability of 173.1 mAh·g^-1at a current density of 4 A·g^-1,and a capacity retention of 92.5%after 1000 cycles^[61]。

the strategy of using MOFs to prepare coatings has effectively alleviated the problem of zinc anode dendrite growth in aqueous zinc-ion batteries,and the intrinsic structural regulation of MOFs materials also provides a new idea for enhancing the storage and transport capacity of zinc ions。

supercapacitors(SCs)consist of a positive electrode,a negative electrode,an electrolyte,and a separator.According to the energy storage mechanism,Supercapacitors can be generally divided into electric double layer capacitors(EDLCs)and pseudocapacitors(Faraday pseudocapacitors)^[62,63]。 For the application of MOFs in SCs,their large specific surface area can enlarge the contact area between the electrolyte and the MOFs electrode,thereby improving the specific capacitance.the adjustable pore size can ensure the rapid transport of electrolyte ions and electrons,and the abundant active sites can improve the pseudocapacitance^[5]。

Sheberla et al.Proposed the use of pure Ni₃(HITP)₂as an active material for EDLCs(Figure 6A),based on the good electrochemical performance of Ni₃(HITP)₂materials,making it the first precedent for pure MOFs materials to be used as electrodes for electric double layer capacitors^[64]。 Liang et al.Mentioned the development strategy of its application in supercapacitor electrode materials in their review on the application of basic MOFs and composite MOFs^[14]。 Most of the basic MOFs are prone to collapse in both acidic and alkaline application environments,so a series of ideas are proposed:(1)the introduction of multi-metals into MOF-74 series helps to improve the redox behavior in cyclic voltammetry and galvanostatic charge-discharge curves;(2)sp²hybridized nitrogen atoms in the ligand can increase the interaction with ions in UiO-based MOFs;(3)nMOF-867 is a suitable sample for both particle and pore size of synthetic nMOF.In addition,in the research of MOFs composites,high conductive materials(such as graphene,GO,rGO,CNTs and conductive polymers)are compounded with the original MOFs to further synthesize MOFs composites,which can improve the conductivity of the original MOFs and accelerate the research of SCs electrode materials^[65]。 In a recent study,Fan et al.introduced Co into MOF-74 and anchored and dispersed Co-MOF-74 nanoparticles on 3D functionalized graphene oxide(FGO)(Fig.6B),and applied it as a negative electrode material in a sodium-ion hybrid capacitor(SIHC).The prepared Co-MOF74|FGO-180 electrode has a high specific capacity of 1170 mAh·g^-1at a current density of 0.1 A·g^-1.The reversible capacity after 100 cycles at a current density of 0.1 A·g^-1was about 416 mAh·g^-1,and the Co-MOF-74|FGO180//AC device exhibited excellent performance(the maximum energy density and power density were 240 Wh·kg^-1and 10 kW·kg^-1,and the cycling stability was excellent)(Figure 6C )^[66]。

Based on the above summary,when MOFs materials are used as electrode materials for alkali metal ion batteries,the electrochemical performance can be effectively improved by regulating the multi-metal synergistic effect,doping of heteroatoms,composite graphene oxide and other strategies.the modified separator made of MOFs materials can be applied to lithium-sulfur batteries to control the shuttle effect of polysulfides;Secondly,MOFs materials can also be used to prepare protective coatings to solve the problems of dendritic growth of anodes in aqueous zinc-ion batteries;MOFs or their composites can be used to prepare electrode materials with high electrochemical performance in supercapacitors.A variety of post-treated materials(doped carbon materials,MOFs/rGO composites,etc.)have been proved to be effective in improving the electrochemical performance of energy storage devices.in addition,some unsaturated coordination States are regulated,and the introduction of amorphous MOFs is also gradually applied in the field of energy storage。

The MOFs obtained by selecting appropriate metal ions and organic ligands for coordination can be directly used in the field of energy storage.In the early research on the application of MOFs materials in lithium storage,Li et al.,inspired by the application of MOF-177 in hydrogen storage,explored its use as an electrode material for lithium storage.They synthesized MOF-177 by solvothermal synthesis and tested it as an anode active material.As a result,the capacity fading rate is very high(the capacity in the first cycle is more than 400 mAh·g^-1,and the capacity in the second discharge process is only 105 mAh·g^-1）.This study opens the way for the subsequent application of MOFs materials in lithium-ion battery electrode materials^[67]。 Since then,MOFs have been widely used in electrode materials research.Maiti et al.Prepared Mn-BTC by solvothermal method and applied it to the anode of lithium-ion battery,and the specific capacity reached 694 mAh·g^-1at the current density of 0.1 A·g^-1[68]。 MOFs with different morphologies,such as microporous Pb-MOF with three-dimensional framework and one-dimensional rhombic channels for lithium-ion anode(Fig.7A),have been obtained by matching various metals with suitable organic ligands.Ti-MOF with stable skeleton and hexagonal nut shape for lithium-ion battery anode(Figure 7 B),cubic cage-like manganese-based MOF(Mn-CCs)(Figure 7 C)are used for lithium-sulfur battery cathode to capture original MOFs such as polysulfides^[69][70][71]。

the properties of MIL series in pristine MOFs have also been extensively studied,and Millange et al.Proposed The first MIL series skeleton:MIL-53 as early as 2002^[72]。 When the MIL series is subsequently applied to energy storage devices,it is found that the pore size and structure of the MIL series need to be regulated by selecting appropriate metal salts and organic ligands,so as to provide a variety of MIL structures,such as rods,spindles,etc.These structures are helpful to retain the original structure when the MIL series is calcined and carbonized as a precursor,or to improve the conductivity and charge storage ability as a basic template for modified materials.For example,Zhu et al.Synthesized disk-shaped MIL-125(Ti)derivative Li_4−xK_xTi₅O₁₂for lithium-ion battery anode,and Zhao et al.Synthesized micron-sized materials based on MIL-88a modified by polyoxometalate for lithium-ion battery anode.Ma et al.First proposed that TB-FeOSC-NS was prepared by calcination under certain conditions using MIL-88 B(Fe)as a self-sacrificial template,and the optimized sheet-like heterostructure enhanced its performance as a lithium-ion anode material,with a high rate capability of 400 mAh·g^-1at a high current density of 20 A·g^{-1[73][74][75]}。 (Table 1 lists some of the original MOFs material applications).In addition,carbon composite MOFs can also be prepared by using composite graphene oxide(GO)and carbon nanotubes as external carbon sources for performance control,for example,MOFs can be grown on carbon materials such as GO and carbon nanotubes(CNTs)to improve electrochemical performance^[76]。 Sung et al.used Co-MOF-74 as an interlayer to composite with multi-walled carbon nanotubes(MWCNTs),and further Used solvothermal method to synthesize Co-MOF-74@MWCNTs as an excellent cathode material for lithium-sulfur batteries^[77]。 In addition,graphene,as a single-atom-thick honeycomb carbon lattice sheet with superior electronic conductivity and high specific surface area,can provide active sites by enhancing the interaction with MOFs。

When MOFs are directly used as electrode materials,they usually have problems such as poor conductivity,easy agglomeration,and poor cycle stability.Researchers usually use MOFs as a precursor template,which is calcined in a protective atmosphere to carbonize the internal organic ligands in situ.the graphitized carbon formed can effectively alleviate the volume change and further enhance the conductivity of the material^[90]。

Appropriate MOFs are selected as precursors,and metal nodes can be transformed into metal compounds(metal oxides,metal sulfides,metal selenides,etc.)Through controlled heat treatment,or further sulfurization,selenization,etc.This kind of metal compound can further enhance the electrochemical performance of MOFs used in energy storage devices while inheriting the original spatial structure of MOFs。