Selective CO2‐to‐CH4 Photoconversion in Aqueous Solutions Catalyzed by Atomically Dispersed Copper Sites Anchored on Ultrathin Graphdiyne Oxide Nanosheets

Photocatalytic conversion of carbon dioxide (CO 2 ) into chemical fuels using sunlight represents an intriguing approach to simultaneously address energy and environmental issues. However, steering the reaction pathways during the photocatalytic reduction of CO 2 to selectively produce desirable hydrocarbon fuels such as methane (CH 4 ) remains a significant challenge. Meanwhile, suppressing the hydrogen evolution reaction is extremely difficult when the photocatalytic process is carried out in aqueous solutions. Herein, ultrathin graphdiyne oxide nanosheets prepared by oxidizing and exfoliating from as‐synthesized graphdiyne are used to activate coordinated Cu 2+ sites without using additional organic ligands for selective reduction of CO 2 to CH 4 in aqueous solutions. It is shown that the reaction selectivity toward CH 4 and CO production can reach 87% and 13%, respectively, whereas the hydrogen evolution reaction can be completely inhibited. The atomically anchored Cu 2+ ions can effectively trap photogenerated electrons and serve as active sites for the selective CO 2 ‐to‐CH 4 conversion. Considering the rich coordination chemistry of polymer materials, the methodology presented in this study can be extended to prepare various polymer‐based photocatalysts with precisely engineered metallic centers toward the selective reduction of CO 2 to chemical fuels.