Selective Photocatalytic Reduction of CO₂ to CO Mediated by Silver Single Atoms Anchored on Tubular Carbon Nitride

Artificial photosynthesis is a promising strategy for converting carbon dioxide (CO2) and water (H2O) into fuels and value-added chemical products. However, photocatalysts usually suffered from low activity and product selectivity due to the sluggish dynamic transfer of photoexcited charge carriers. Herein, we describe anchoring of Ag single atoms on hollow porous polygonal C3N4 nanotubes (PCN) to form the photocatalyst Ag-1@PCN with Ag-N-3 coordination for CO2 photoreduction using H2O as the reductant. The as-synthesized Ag-1@PCN exhibits a high CO production rate of 0.32 mu mol h(-1) (mass of catalyst: 2 mg), a high selectivity (>94 %), and an excellent stability in the long term. Experiments and density functional theory (DFT) reveal that the strong metal-support interactions (Ag-N-3) favor *CO2 adsorption, *COOH generation and desorption, and accelerate dynamic transfer of photoexcited charge carriers between C3N4 and Ag single atoms, thereby accounting for the enhanced CO2 photoreduction activity with a high CO selectivity. This work provides a deep insight into the important role of strong metal-support interactions in enhancing the photoactivity and CO selectivity of CO2 photoreduction.