H-Bond-Mediated Selectivity Control of Formate versus CO during CO2 Photoreduction with Two Cooperative Cu/X Sites

It is highly desirable to achieve solar-driven conversion of CO2 to valuable fuels with controlled selectivity. The existing catalysts are mainly explored for CO production but rarely for formate generation. Herein, highly selective photoreduction of CO2 to formate (99.7%) was achieved with a high yield of 3040 μmol g–1 in 10 h by hierarchical integration of photosensitizers and monometallic bpy-Cu/ClX (X = Cl or adenine) catalysts into a stable Eu-bpy metal–organic framework. However, replacing X with pyridine in bpy-CuCl/X significantly reduced formate production while increasing the CO yield to 960 μmol g–1. Systematic investigations revealed that the catalytic process is mediated by the H-bond synergy between Cu-bound X and CO2-derived species, and the selectivity of HCOO– can be controlled by simply replacing the coordination ligands. This work provides a molecularly precise structural model to provide mechanistic insights for selectivity control of CO2 photoreduction.