Metal–organic frameworks (MOFs) have recently
emerged as
promising electrocatalysts because of their atomically dispersed metal
sites and porous structures. The active sites of MOF catalysts largely
exist as coordinatively unsaturated metal sites (CUMSs). In this study,
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 the plasma-engraving species, intensity,
and duration. The electrochemical activity of the engraved MOF is
found to be quantitatively correlated to the coordination geometry
of the metal centers corresponding to CUMSs. Specifically, the hydrogen
plasma-engraved Co-MOF-74 shows an 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 CUMS control strategy and the revealed CUMSs activity
correlation can inspire the further microstructure tuning of MOFs
for various applications.