Engineering Coordination Environment of Cobalt Center in Molecular Catalysts for Improved Photocatalytic CO2 Reduction

The creation of effective and inexpensive catalysts is essential for photocatalytic CO2 reduction. Homogeneous molecular catalysts, possessing definite crystal structures, are desirable to study the relationship between catalytic performance and coordination microenvironment around catalytic center. In this report, we elaborately developed three Co(II)-based molecular catalysts with different coordination microenvironments for CO2 reduction, named [CoN3O]ClO4, [CoN4]ClO4, and [CoN3S]ClO4, respectively. The optimal [CoN3O]ClO4 photocatalyst has a maximum TON of 5652 in photocatalytic reduced CO2 reduction, which is 1.28 and 1.65 times greater than that of [CoN4]ClO4 and [CoN3S]ClO4, respectively. The high electronegativity of oxygen in L1 (N,N-bis(2-pyridylmethyl)-N-(2-hydroxybenzyl)amine) provides the Co(II) catalytic centers with low reduction potentials and a more stable *COOH intermediate, which facilitates the CO2-to-CO conversion and accounts for the high photocatalytic activity of [CoN3O]ClO4. This work provides researchers new insights in development of catalysts for photocatalytic CO2 reduction. © 2023 SIOC, CAS, Shanghai, & WILEY-VCH GmbH.