Embedding Metallosalen Active Sites in Zr-MOF for Enhanced Selective Syngas Production from CO Photoreduction.

Selective photocatalytic CO reduction to product syngas remains a great challenge. Herein, we proposed a novel strategy by integration of metallosalen (M-Salen) active sites and Zr-MOF, to promote the selective production of syngas through photocatalytic CO and HO reduction. A series of M-Salen (Co, Co, Cu, Cu) with carboxylic groups were embedded into a Zr-MOF (NKM-908) by replacing the terminal coordinated -OH/HO on the Zr clusters. The integration of M-Salen and NKM-908 significantly accelerate the transfer dynamics of photogenerated charge and promote CO enrichment around the M-Salen active sites. The M-Salen sites played a crucial role in enhancing CO production. Specifically, the mononuclear Co-Salen exhibits stronger CO adsorption and activation capabilities than the binuclear Co-Salen, with enhanced *CO coverage. In addition, the Co-based salen catalyst exhibits a lower energy barrier for *CO desorption-the rate-determining step-compared to its Cu-based counterpart. As a result, the Co-NKM-908 exhibited optimal performance in photocatalytic CO and HO conversion, achieving a high CO production rate of 1.92 mmol g h and a H production rate of 1.52 mmol g h with a standard syngas CO/H ratio of 1.3/1.