Excellent Supercapacitor Performance of Robust Nickel–Organic Framework Materials Achieved by Tunable Porosity, Inner-Cluster Redox, and in Situ Fabrication with Graphene Oxide

Metal–organic frameworks have shown promising applications as electrode materials for supercapacitors because of the high porosity and tunable structures, but their poor water stability and conductivity limit their capacitance and efficiency. To demonstrate how to overcome these drawbacks, three isostructural Ni–organic frameworks with [NiII2NiIII(μ3-OH)(COO)6] trinuclear building blocks are selected. Taking advantage of high-connected architectures, absence of open metal sites, and effective inner-cluster redox process, three Ni–organic frameworks all are stable in KOH electrolyte and exhibit a pseudo-capacitor behavior with high specific capacitances up to 394, 426, and 465 F g–1. The increasing porosity facilitates the diffusion of metal ions and electrons and thus increases their electrochemical performance. Furthermore, we demonstrate that the in situ fabrication of metal–organic frameworks with graphene oxide can effectively promote their supercapacitor performance. With a given 3% graphene oxide do...