Photoreduction of CO2 to complete CO catalyzed by charge-density-regulating metal-organic frameworks

Abstract

Photoreduction of CO₂ to a single gas product requires catalysts with remarkable product selectivity because CO and CH₄ are usually produced simultaneously. We propose that the charge-density regulation within metal-organic frameworks (MOFs) could effectively manage the binding energy required for reduction intermediates, thereby controlling the ultimate product formation to obtain CO with 100% selectivity. Herein, two iso-structured Fe-based MOFs bearing linkers with different electronic properties were prepared and exhibited favorable CO₂ photoreduction performance without any cocatalyst or photosensitizer. In particular, the linker was altered to reduce the transfer of charges from Fe to the surrounding ligands, regulating the charge-density distribution. The binding affinity with the key COH∗ was remarkably weakened and behaved thermodynamically unfavorably compared with CO desorption, resulting in 100% CO generation. These insights provide a catalyst design strategy for controlling reduction species and improving product selectivity, which could encourage the development of intriguing MOF material customization for photocatalysis.