Porous C3N4 nanosheet supported Au single atoms as an efficient catalyst for enhanced photoreduction of CO2 to CO

Artificial photosynthesis utilizing solar energy to convert carbon dioxide (CO2) and water (H2O) into fuels and high-value chemicals offers a promising technology for mitigating energy consumption and environmental pollution. However, the development of efficient photocatalysts with high product selectivity remains a big challenge due to the sluggish dynamic transfer of photogenerated charge carriers. Herein, porous C3N4 nanosheet supported Au single atoms photocatalyst (Au1@CN) with Au-N4 coordination is fabricated via a facile "impregnation + freeze-drying" process. The as-synthesized Au1@CN exhibits efficient and stable CO2 photoreduction activity with a CO evolution rate of 0.58 mu mol h-1 (amount of catalyst: 10 mg), CO selectivity of 94 %, and a turnover frequency (TOF) of 10.0 h-1 using H2O as the reductant, which exceed most previous works on C3N4-based single-atom photocatalysts for CO2 reduction. Experimental studies and density functional theory (DFT) calculations reveal that the unique Au-N4 coordination promotes the dynamic transfer of photogenerated charge carriers, facilitates the adsorption/activation of CO2 molecules and generation of *COOH intermediate, thereby significantly enhancing the CO2 photoreduction activity with high CO selectivity. This study demonstrates an effective strategy for the design of M-N4 coordinated single-atom catalyst toward efficient and selective photoreduction of CO2 to CO.