Two-dimensional electrically conductive metal-organic frameworks (MOFs) have emerged as promising model electrodes for use in electric double-layer capacitors (EDLCs). However, a number of fundamental questions about the behaviour of this...

Metal-organic frameworks (MOFs) are among the most promising materials for next-generation energy storage systems. However, the impact of particle morphology on the energy storage performances of these frameworks is poorly...

Electroconductive metal–organic frameworks (MOFs) have emerged as high-performance electrode materials for supercapacitors, but the fundamental understanding of the underlying chemical processes is limited. Here, the electrochemical interface of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with an organic electrolyte is investigated using a multiscale quantum-mechanics/molecular-mechanics (QM/MM) procedure and experimental electrochemical measurements. Our simulations reproduce the observed capacitance values and reveals the polarization phenomena of the nanoporous framework. We find that excess charges mainly form on the organic ligand, and cation-dominated charging mechanisms give rise to greater capacitance. The spatially confined electric double-layer structure is further manipulated by changing the ligand from HHTP to HITP (HITP = 2,3,6,7,10,11-hexaiminotriphenylene). This minimal change to the electrode framework not only increases the capacitance but also increases the self-diffusion coefficients of in-pore electrolytes. The performance of MOF-based supercapacitors can be systematically controlled by modifying the ligating group.

Two-dimensional electrically conductive metal-organic frameworks (MOFs) are candidate electrode materials for use in electric double-layer capacitor (EDLC) structure-property investigations due to their well-defined crystalline structures. Their promising capacitive performance was first illustrated by EDLCs constructed with the layered framework Ni₃(HITP)₂(HITP = 2,3,6,7,10,11-hexaiminotriphenylene) and an organic electrolyte. Despite this promise, there have been few follow-up studies on the use of these frameworks in EDLCs, raising questions about the generality of the results. Here, we demonstrate the high capacitive performance of the layered framework Cu₃(HHTP)₂ (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) in EDLCs with an organic electrolyte and compare its performance with Ni₃(HITP)₂. Cu₃(HHTP)₂ exhibits a specific capacitance of 110 – 114 F g^–1at low current densities of 0.04 – 0.05 A g^–1 and shows modest capacitance retentions (66 %) at current densities up to 2 A g^–1, mirroring the performance of Ni₃(HITP)₂. However, we also explore the limitations of Cu₃(HHTP)₂ in EDLCs, finding a limited cell voltage window of 1.3 V and only moderate capacitance retention over 30,000 cycles. This illustrates that these materials require further development to improve their EDLC performance, particularly to reach similar cycling performance levels as porous carbons. Despite this, our work underscores the utility of framework materials in EDLCs and suggests that capacitive performance is largely independent of the identity of the metal node and organic linker molecule, instead being dictated by the three-dimensional structure of the framework. These important insights will aid the design of future conductive MOFs for use in EDLCs.

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