Conductive metal-organic frameworks for electrochemical energy conversion and storage

Frames low charge conductivity as the obstacle for pristine MOFs and positions electron- and proton-conductive MOFs as a direct design strategy for electrochemical applications.

Relevance: Core · p001 · Abstract

Restates the central thesis that intrinsic conductivity enables more direct use of pristine MOFs, while the field remains limited by narrow design strategies and incomplete practical testing.

Relevance: Core · p006 · Conclusion

Reviews conductive MOFs as electrocatalysts or conductive hosts for ORR, OER, HER, overall water splitting and Zn-air batteries, emphasising active-site exposure and electron transfer.

Relevance: Core · p002 · Conductive MOFs for electrochemical energy conversion · Table 1

Defines MOFs, explains why electron and proton conductivity matter for electrochemical performance, and contrasts pristine conductive MOFs with pyrolysed derivatives and additive-loaded composites.

Relevance: Core · p001 · Introduction · Fig. 1

Organises charge transport into electron and proton conduction, with electronic hopping/band transport mapped onto through-bond and through-space design, and proton transport mapped onto Grotthuss and vehicle mechanisms.

Relevance: Core · p001-p002 · Mechanisms of charge conductions in MOFs · Figs. 2-3

Discusses proton-conductive MOFs in hybrid PEMs for H2-PEMFCs and DMFCs, highlighting porous channels, surface functional groups, polymer interfaces and water retention.

Relevance: Core · p005 · Conductive MOFs for proton exchange membranes · Table 3

Identifies non-scalable synthesis, cost, reliance on carbonisation, limited application testing, and narrow ligand/functionality diversity as future challenges.

Relevance: Core · p006 · Prospects and challenges

Covers supercapacitors, metal-ion batteries, hybrid storage and metal-sulphur batteries, where intrinsic conductivity can reduce dead mass from conductive agents and binders.

Relevance: Core · p003 · Conductive MOFs for electrochemical energy storage · Table 2

Electrochemical application domains

The review's application structure separates electrocatalytic conversion reactions, electrode/separator roles in storage devices, and proton-conducting membranes for fuel cells.

Categories: energy conversion · energy storage · proton exchange membranes

p002-p005 · Electrochemical applications of conductive MOFs · Fig. 1

Charge-carrier type in conductive MOFs

The review separates conductive MOFs by whether electrochemical performance depends primarily on electron transfer through framework structures or proton transport through pores and interfaces.

Categories: electron-conductive MOFs · proton-conductive MOFs

p001 · Mechanisms of charge conductions in MOFs

Electronic pathway design

Through-bond conduction relies on metal-ligand orbital overlap and covalent coordination pathways, whereas through-space conduction relies on non-covalent interactions such as pi-pi stacking between adjacent ligands.

Categories: through-bond · through-space

p001-p002 · Mechanisms of charge conductions in MOFs · Fig. 2

Electronic transport mechanisms

Electronic conduction is described either as carrier hopping between neighbouring sites or as delocalised band-like transport.

Categories: hopping transport · band transport

p001 · Mechanisms of charge conductions in MOFs

Proton conduction mechanisms

Grotthuss transport proceeds through hydrogen-bond making and breaking, while vehicle transport moves protons as part of molecular complexes such as hydronium species.

Categories: Grotthuss mechanism · vehicle mechanism

p002 · Mechanisms of charge conductions in MOFs · Fig. 3

Conductive MOF roles in storage

For energy storage the review distinguishes direct electrode use, growth or loading with supporting substrates and hosts, and separator modification for Li-S batteries.

Categories: sole electrode material · composite electrode or host · separator coating

p005 · Metal-sulphur batteries · Fig. 10

Dense 2D conductive MOFs using hexaaminobenzene linkers with Ni, Cu or Co nodes.

Conduction: Strong conjugated interactions between ligand pi orbitals and metal d orbitals support intrinsic electrical conductivity and redox-active M-N4 sites.

Representative materials: Ni-HAB · Cu-HAB · Co-HAB

Nodes / linkers: Ni · Cu · Co · HAB

p004 · Supercapacitors · Fig. 7

Ni-based 2D conductive MOFs using hexaiminohexaazatrinaphthalene ligands to combine Ni-N4 framework linkages with unsaturated Ni-N2 sites.

Conduction: Ni-N4 linkages support 2D pi-conjugation and conductivity, while Ni-N2 sites increase proton binding for HER.

Representative materials: Ni3(Ni3.HAHATN)2

Nodes / linkers: Ni · HAHATN

p003 · Hydrogen evolution reaction · Fig. 6

Conductive MOFs built from hexahydroxytriphenylene-derived catecholate linkers and transition-metal centres.

Conduction: Metal-catecholate coordination contributes to intrinsic electrical conductivity, redox-active sites and open channels for ion transport.

Representative materials: Co0.27Ni0.73-CAT · Fe1Ni4-HHTP · Cu3(HHTP)2 · Co3(HHTP)2

Nodes / linkers: Co · Ni · Fe · Cu · HHTP · catecholate

p006 · Conclusion · Tables 1-2

MOFs using hexaiminotriphenylene-type ligands to form 2D conjugated frameworks with transition-metal nodes.

Conduction: In-plane delocalised pi-d conjugation and square-planar metal-nitrogen coordination provide electronic conduction and active sites.

Representative materials: Ni3(HITP)2 · Co3(HITP)2 · La0.6Sr0.4Co0.8Fe0.2O3@Ni3(HITP)2 · Ni3(HITP)2/PP

Nodes / linkers: Ni · Co · perovskite-supported Co/Fe oxide · HITP

p002 · Oxygen reduction reaction · Fig. 4; Tables 1-2

Cr-based MIL-101 blended with chitosan after ligand sulfonation or non-volatile acid loading.

Conduction: Acid groups, water hydrogen-bond networks and chitosan amino groups form interfacial donor-acceptor pathways for proton hopping.

Representative materials: CS/S-MIL-101 · CS/H2SO4@MIL-101 · CS/H3PO4@MIL-101 · CS/CF3SO3H@MIL-101

Nodes / linkers: Cr · terephthalic acid · 2-sulfoterephthalic acid

p005-p006 · Conductive MOFs for proton exchange membranes · Fig. 12; Table 3

Zr-fumarate MOF-801 blended with polymer matrices or functionalised with imidazole species for proton exchange membranes.

Conduction: Hydrogen-bond networks from Zr-OH and carboxylate groups support Grotthuss transport; imidazole functionalisation adds vehicle and Grotthuss pathways.

Representative materials: MOF-801/PVDF-PVP · Im@MOF-801 · Im-MOF-801 · C-SPAEKS/Im-MOF-801

Nodes / linkers: Zr · fumaric acid · imidazole-functionalised fumarate MOF

p005 · Conductive MOFs for proton exchange membranes · Fig. 11; Table 3

Tetrathiafulvalene tetrabenzoate MOFs in which stacked TTF units generate through-space charge-transport pathways.

Conduction: Short S-S interactions and pi-pi stacking between TTF moieties enhance orbital overlap and intrinsic charge mobility.

Representative materials: Zn2(TTFTB) · Cd2(TTFTB) · La4(TTFTB)3 · Co2(TTFTB) · Mn2(TTFTB)

Nodes / linkers: Zn · Cd · La · Co · Mn · TTFTB · tetrathiafulvalene

p002 · Mechanisms of charge conductions in MOFs · Fig. 2

Amino-functionalised UiO-66 combined with sulfonated poly(ether sulfone) nanofibres and Nafion matrix for DMFC membranes.

Conduction: SO3H and NH2 acid-base pairs provide proton-hopping sites while hydrophilic pores retain water for vehicle transport.

Representative materials: UiO-66-NH2@NFs · UiO-66-NH2@SPES/Nafion

Nodes / linkers: Zr · 2-aminoterephthalic acid

p006 · Conductive MOFs for proton exchange membranes · Fig. 12; Table 3

Bimetallic conductive MOF tuning

Introduce two metal elements into conductive frameworks to combine catalytic functions or tune charge-transfer and reaction-intermediate energetics.

Claimed effects: Can combine strengths of monometallic counterparts and improve electrocatalytic metrics such as ORR onset, OER overpotential and charge-transfer resistance.

Controlling variables: metal ratio · substitution level · active-site identity · charge-transfer resistance

Representative materials: Co0.27Ni0.73-CAT · Fe1Ni4-HHTP

Caveat: Still inherits the review's broader limitation that many applied examples use a narrow set of ligands and framework structures.

p002-p003 · Oxygen reduction reaction; Oxygen evolution reaction · Figs. 4-5

Conductive MOFs as hosts or shells for active species

Use conductive MOFs to host catalytic species or sulphur/polysulphide phases, or to coat active oxides, so the MOF supplies porosity and charge-transfer pathways.

Claimed effects: Can replace carbonised derivatives or conductive carbon while adding specific interactions, confinement or surface-electronic modification.

Controlling variables: host pore size · active-species loading · interfacial bonding · short- and long-range conduction networks

Representative materials: Co3O4/Cu3(HHTP)2 · S@Ni3(HITP)2-CNT · Ni3(HITP)2/PP

Caveat: External supports and binders can complicate attribution of performance solely to the MOF.

p003-p005 · Hydrogen evolution reaction; Metal-sulphur batteries · Figs. 6 and 10

Growth on conductive or flexible substrates

Grow conductive MOF nanorods or nanoarrays on patterned carbon, polypyrrole membranes, cellulose nanofibres or carbon nanotube fibres.

Claimed effects: Improves device integration for microsupercapacitors, flexible capacitors and wearable Zn-ion batteries.

Controlling variables: substrate conductivity · mechanical flexibility · MOF morphology · direct-write patterning

Representative materials: Ni-CAT/LSG · Cu-CAT/PPy · Ni-HHTP/cellulose nanofibres · MIL-47@CNTF

Caveat: Composite device performance may depend strongly on substrate properties as well as intrinsic MOF conductivity.

p004 · Supercapacitors; Metal-ion batteries · Figs. 8-9

Design pristine intrinsically conductive MOFs

Use metal-ligand combinations and framework architectures that generate intrinsic electronic or protonic conductivity while retaining porosity and coordination-framework identity.

Claimed effects: Bypasses high-temperature carbonisation and reduces reliance on conductive additives while preserving porous-framework benefits.

Controlling variables: metal-ligand combination · framework dimensionality · conjugated linker choice · functional group identity

Representative materials: Ni3(HITP)2 · Co3(HITP)2 · MOF-801 · UiO-66-NH2@SPES/Nafion

Caveat: The review stresses that practical testing and design diversity remain limited.

p001 · Introduction

Functional-group engineering for MOF/polymer PEMs

Use pristine linkers, modified ligands or external acid/base species to create proton carriers, hydrogen-bond networks and water-retaining channels at MOF-polymer interfaces.

Claimed effects: Improves proton conductivity and membrane stability by combining Grotthuss hopping sites with vehicle-mediated water pathways.

Controlling variables: acid or base functional group · polymer matrix · humidity · MOF-polymer interface · water retention

Representative materials: C-SPAEKS/Im-MOF-801 · CS/H2SO4@MIL-101 · UiO-66-NH2@SPES/Nafion · MOF-1/Aquivion

Caveat: The review notes that many proton-conductive MOF papers report conductivity but not direct fuel-cell power-density tests.

p005-p006 · Conductive MOFs for proton exchange membranes · Figs. 11-12; Table 3

Through-bond electronic pathway construction

Select redox-active metal nodes and conjugated ligands whose orbitals overlap through coordination bonds.

Claimed effects: Creates covalent metal-organic pathways for electron transport and allows active-site chemistry to be tuned through metal substitution.

Controlling variables: metal redox state · ligand conjugation · metal-ligand orbital overlap · coordination geometry

Representative materials: Cu[Cu(pdt)2] · Cu[Ni(pdt)2] · Ni3(HITP)2

Caveat: Metal substitution can substantially reduce conductivity when the substituted centre supplies fewer high-energy electrons.

p001 · Mechanisms of charge conductions in MOFs · Fig. 2

Through-space pi-stacking pathway construction

Use non-covalent interactions, especially pi-pi stacking between adjacent ligands, to provide charge-transfer pathways without relying solely on bonded connectivity.

Claimed effects: Enhances orbital overlap and charge mobility in frameworks such as TTFTB-based MOFs.

Controlling variables: stacking distance · ligand planarity · S-S or pi-pi contacts · columnar packing

Representative materials: Zn2(TTFTB) · M2(TTFTB)

Caveat: Presented mainly as mechanistic design logic; the review gives fewer electrochemical performance examples for this family.

p002 · Mechanisms of charge conductions in MOFs · Fig. 2

Reports on conductive MOF performance and mechanisms in electrochemical applications remain limited relative to design and synthesis studies.

Proposed direction: Expand mechanistic application studies across more electrochemical reactions and device architectures.

p006 · Prospects and challenges

Many MOF systems still require high-temperature carbonisation to obtain adequate charge conductivity.

Proposed direction: Design intrinsically conductive pristine MOFs that avoid carbonisation and retain crystalline framework advantages.

p006 · Prospects and challenges

Conductive COFs face similar low-conductivity limitations and are emerging in parallel with conductive MOFs.

Proposed direction: Use MOF lessons cautiously as comparative framing for conductive COFs in electrochemical contexts.

p006 · Prospects and challenges

Many studies report MOF conductivity but do not directly test PEMFC, electrolyser, battery or metal-air cell performance.

Proposed direction: Prioritise direct device-level testing to establish practical competitiveness over non-conductive MOFs and derivatives.

p006 · Prospects and challenges

Current applied conductive-MOF research uses similar ligands, framework structures and functional groups.

Proposed direction: Explore more metal-ligand combinations, functional groups and charge-transport pathways beyond HAB, HITP, HHTP, sulfonate and amino motifs.

p006 · Prospects and challenges

Practical MOF applications are impeded by non-scalable laboratory synthesis and high material costs.

Proposed direction: Develop scalable, lower-cost conductive MOF syntheses that preserve intrinsic conductivity and porosity.

p006 · Prospects and challenges