Fine-tuning the coordinatively unsaturated metal sites of metal-organic framework by plasma engraving for enhanced electro-catalytic activity

ABSTRACT: Metal-organic frameworks (MOFs) have recently emerged as promising electrocatalysts due to their atomically dispersed metal sites and porous structures. The active sites of MOFs catalysts largely exist as the coordinatively unsaturated metal sites (CUMSs). In this study, the facile microwave-induced plasma engraving is applied to fine-tune the CUMSs of cobalt-based MOF (Co-MOF-74) without destroying its phase integrity by controlling plasma engraving species, intensity, and duration. The electrochemical activity of engraved MOF is found to be quantitatively correlated to the coordination geometry of metal centers corresponding to CUMSs. Specifically, the hydrogen plasma engraved Co-MOF-74 shows enhanced catalytic activity of oxygen evolution reaction, which exhibits a low overpotential (337 mV at 15 mA cm-2), high turnover frequency (0.0219 s-1), and large mass activity (54.3 A g-1). The developed CUMSs-control strategy and revealed CUMSs-activity correlation can inspire the further microstructu...