Parallel-Type *CO Adsorption Tuning Steers Efficient Photocatalytic CO2 Methanation

Abstract

Photocatalytic reduction of carbon dioxide (CO2) to methane (CH4) represents a promising route for renewable energy storage, yet it suffers from low efficiency. The challenge exists in the key *CO intermediate adsorption behavior, in which the typically top-bonded *CO favors CO release, resulting in dominant syngas (CO and H2) products. Herein, we demonstrate an intermediate adsorption tuning strategy via a Zn–P–Cd coordinated photocatalyst (denoted as P–Cd4ZnS5), in which the diffuse 3p orbital of the coordinated P site enables close P–O overlap with the oxygen end of *CO, thus leading to a parallel *CO configuration by simultaneously forming P–O and Zn–C bonds. Moreover, the stabilized parallel-type *CO subsequently undergoes hydrogenation at adjacent Cd sites to yield *CHO intermediates toward the CH4 reaction pathway. As a result, the optimized P–Cd4ZnS5 achieves an efficient CO2-to-CH4 conversion under ambient light irradiation at 120 mW cm–2, including a high selectivity of ∼93.8%, a CH4 production rate of ∼366 μmol g–1 h–1, and a sustained stability of >120 h, substantially exceeding most of the previous reports. Our work proposes an attractive strategy to tune parallel-type *CO adsorption for steering photocatalytic CO2 reduction toward deep-reduction products with high efficiency, selectivity, and stability.