Cu-doped mesoporous SnO nanoparticles with rich grain boundaries and oxygen vacancies for photocatalytic CO-to-CO conversion.

Photocatalytic conversion of carbon dioxide into fuels provides an effective approach to realize carbon resource utilization. However, the photocatalytic efficiency is still relatively low due to the recombination of photogenerated charges. Herein, we have designed Cu-doped SnO nanoparticles (Cu-SnO) using a glucose-involved hydrothermal crystallization method for the photocatalytic reduction of CO. The rich oxygen vacancies facilitated the separation and transfer of photogenerated charges, and the confined effect of the typical mesoporous structure promoted the adsorption of CO, especially a high density of grain boundaries (GBs) and the doping of atomic Cu would introduce new active sites to activate CO molecules. This elaborately designed catalyst exhibited super and stable photocatalytic conversion activity of CO-into-CO, with a CO optimal yield of 107 µmol g in 4 h, which was 2.75 times that over pure SnO. Raman results indicated that the CO reduction reaction followed a *COOH pathway on Cu-SnO. This work provides implications for the construction of a catalyst with rich defects in the field of energy and environmental catalysis.