Ligand-based modulation of the electronic structure at metal nodes in MOFs to promote the oxygen evolution reaction

Abstract

Exploring and designing efficacious metal–organic framework (MOF) electrocatalysts may unravel the thorny aspects limiting oxygen evolution reaction (OER) with molecular accuracy. Optimizing the design of metal nodes and linking ligands of MOFs permits tuning the electron cloud density of intrinsic catalytic centers for addressing their inherent low conductivity properties with the aim of accelerating catalytic performance. Herein, the electrocatalytic properties of representative imidazole ligand-controlled ZIF materials with electron-absorbing or electron-donating groups were systematically investigated to reveal the effect of the ligand mechanism on the performance of the oxygen evolution reaction (OER). Further characterization and experiments indicated that 2-nitroimidazole (2-nIm) could reduce the electron cloud density of Co sites to promote the formation of active *OOH species that adsorbed on Co sites, which exhibited remarkable electrocatalytic activity with an overpotential of 284 mV at 50 mA cm⁻² and a Tafel slope of 151 mV dec⁻¹. This work presents a benchmark for electronic structure engineering of metal nodes through ligand tuning and points the way to the design of efficient MOF catalysts.