Exposing coordination-unsaturated Co sites in Co-MOF for efficient photocatalytic water oxidation

Abstract

Water oxidation to molecular dioxygen driven by visible light is essential but difficult in solar fuel production due to its sluggish reaction kinetics. Although the catalytic process is highly dependent on the coordination-unsaturated metal sites in coordination catalysts, the controllable design of catalysts with such catalytic sites remains challenging. Herein, we report two new Co-MOFs (CoBIM-1 and CoBIM-2) for photocatalytic water oxidation under visible light. The coordination environment of Co in Co-MOFs can be easily manipulated by changing the atmosphere and concentration of deprotonated solvent during synthesis. CoBIM-1 with coordinatively unsaturated Co sites showed good performance with an O₂ production of 2.0 mmol g⁻¹ h⁻¹, in sharp contrast to its counterpart CoBIM-2. Furthermore, through isotope tracing experiments, we confirmed that the dioxygen was produced from water oxidation. This work highlights that the atmosphere during synthesis and solvent selection greatly regulate the crystal structures of MOFs and further manipulate their photocatalytic performance.