Selective Photocatalytic Reduction of CO 2 to CO Mediated by Silver Single Atoms Anchored on Tubular Carbon Nitride.

Artificial photosynthesis is a promising strategy for converting carbon dioxide (CO 2 ) and water (H 2 O) 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 C 3 N 4 nanotubes (PCN) to form the photocatalyst Ag 1 @PCN with Ag-N 3 coordination for CO 2 photoreduction using H 2 O as the reductant. The as-synthesized Ag 1 @PCN exhibits a high CO production rate of 0.32 μmol 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 *CO 2 adsorption, *COOH generation and desorption, and accelerate dynamic transfer of photoexcited charge carriers between C 3 N 4 and Ag single atoms, thereby accounting for the enhanced CO 2 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 CO 2 photoreduction.