Aerobic oxidation of a covalent organic framework facilitating photocatalytic CO2 reduction with water†

Photocatalytic CO₂ reduction offers a promising approach for solar-to-chemical energy conversion. Achieving CO₂ reduction under an aerobic environment is challenging, primarily owing to the competitive O₂ reduction reaction at metal active sites. Herein, we demonstrate a hybrid photocatalyst of N₃-COF/MoS₂, where an azine-linked COF serves as a metal-free active site for CO₂ reduction. The hybrid exhibits enhanced catalytic performance in CO₂ reduction under aerobic conditions. At 20% O₂ concentration, close to the atmospheric O₂ content, the CO production rate reaches 28 μmol g⁻¹ h⁻¹, which is much higher than that obtained using pure CO₂. Structural, in situ spectroscopic and computational analyses reveal that the oxidation of azine groups in the COF by O₂ induces the formation of highly active radical intermediates, which can suitably and preferentially react with CO₂, resulting in the enhanced CO₂ reduction performance in the presence of O₂. This work provides a fresh insight into designing photocatalysts applied under ambient conditions for solar energy conversion.