Microscopic Origin of Electrochemical Capacitance in Metal-Organic Frameworks

SJ Shin and JW Gittins and MJ Golomb and AC Forse and A Walsh, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 145, 14529-14538 (2023).

DOI: 10.1021/jacs.3c04625

Electroconductivemetal-organic frameworks (MOFs)have emergedas high- performance electrode materials for supercapacitors, but thefundamental understanding of the underlying chemical processes islimited. Here, the electrochemical interface of Cu-3(HHTP)(2) (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with an organicelectrolyte is investigated using a multiscale quantum-mechanics/molecular- mechanics(QM/MM) procedure and experimental electrochemical measurements. Oursimulations reproduce the observed capacitance values and revealsthe polarization phenomena of the nanoporous framework. We find thatexcess charges mainly form on the organic ligand, and cation- dominatedcharging mechanisms give rise to greater capacitance. The spatiallyconfined electric double-layer structure is further manipulated bychanging the ligand from HHTP to HITP (HITP = 2,3,6,7,10,11-hexaiminotriphenylene).This minimal change to the electrode framework not only increasesthe capacitance but also increases the self-diffusion coefficientsof in-pore electrolytes. The performance of MOF-based supercapacitorscan be systematically controlled by modifying the ligating group.

Return to Publications page