Conductive metal-organic frameworks with wheel-shaped metallomacrocycle subunits as high-performance supercapacitor electrodes

Abstract

The poor conductivities of metal–organic frameworks (MOFs) hinder their direct application as supercapacitor electrode materials. Here, a conductive MOF, MWM-1 (Co/2Ni) ([Co(III)3Ni(III)3Co(II)2Ni(II)2(mba)12(Hdtba)2(H2O)8]n, Hdtba = 2,2́-dithiodibenzoic acid monovalent anion, mba = 2-mercaptobenzoic acid divalent anion), with wheel-shaped metallomacrocyclic subunits, is synthesised using inexpensive H2mba as the ligand. Unlike that of two-dimensional conductive MOFs produced using expensive conductive ligands, the conductivity of MWM-1 (Co/2Ni) originates from the partial replacement of Co(III)/Co(II) ions with Ni(III)/Ni(II) ions in the original molecular metallomacrocyclic backbone. The single-crystal structure of MWM-1 (Co/2Ni) reveals that Ni incorporation does not alter the overall molecular structure of the non-conductive MWM-1 (Co) ([Co(III)3Co(II)2(mba)6(Hdtba)(H2O)4]n) precursor. Studies on the magnetic and conductive properties of MWM-1 (Co/2Ni) and MWM-1 (Co) indicate that Ni doping of MWM-1 (Co) significantly improves its conductivity and, thus, its performance as an electrode material for supercapacitors. This study provides a novel strategy for constructing conductive MOFs, advancing the applicability of MOF materials in energy storage.