Boosting CO2 Photoreduction to Formate or CO with High Selectivity over a Covalent Organic Framework Covalently Anchored on Graphene Oxide

Abstract Covalent organic frameworks (COFs) have been widely studied in photocatalytic CO 2 reduction reaction (CO 2 RR). However, pristine COFs usually exhibit low catalytic efficiency owing to the fast recombination of photogenerated electrons and holes. In this study, we fabricated a stable COF‐based composite (GO‐COF‐366‐Co) by covalently anchoring COF‐366‐Co on the surface of graphene oxide (GO) for the photocatalytic CO 2 reduction. Interestingly, in absolute acetonitrile (CH 3 CN), GO‐COF‐366‐Co shows a high selectivity of 94.4 % for the photoreduction of CO 2 to formate, with a formate yield of 15.8 mmol/g, which is approximately four times higher than that using the pristine COF‐366‐Co. By contrast, in CH 3 CN/H 2 O ( v : v =4 : 1), the main product for the photocatalytic CO 2 reduction over GO‐COF‐366‐Co is CO (96.1 %), with a CO yield as high as 52.2 mmol/g, which is also approximately four times higher than that using the pristine COF‐366‐Co. Photoelectrochemical experiments demonstrate the covalent bonding of COF‐366‐Co and GO to form the GO‐COF‐366‐Co composite facilitates charge separation and transfer significantly, thereby accounting for the enhanced catalytic activity. In addition, theoretical calculations and in situ Fourier transform infrared spectroscopy reveal H 2 O can stabilize the *COOH intermediate to further form a *CO intermediate via O−H(aq)⋅⋅⋅O(*COOH) hydrogen bonding, thus explaining the regulated photocatalytic performance.