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.