Spatial confinement of copper single atoms into covalent triazine-based frameworks for highly efficient and selective photocatalytic CO2 reduction

Converting CO2 into carbonaceous fuels via photocatalysis represents an appealing strategy to simultaneously alleviate the energy crisis and associated environmental problems, yet designing with high photoreduction activity catalysts remains a compelling challenge. Here, combining the merits of highly porous structure and maximum atomic efficiency, we rationally constructed covalent triazine-based frameworks (CTFs) anchoring copper single atoms (Cu-SA/CTF) photocatalysts for efficient CO2 conversion. The Cu single atoms were visualized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images and coordination structure of Cu-N-C-2 sites was revealed by extended X-ray absorption fine structure (EXAFS) analyses. The as-prepared Cu-SA/CTF photocatalysts exhibited superior photocatalytic CO2 conversion to CH4 performance associated with a high selectivity of 98.31%. Significantly, the introduction of Cu single atoms endowed the Cu-SA/CTF catalysts with increased CO2 adsorption capacity, strengthened visible light responsive ability, and improved the photogenerated carriers separation efficiency, thus enhancing the photocatalytic activity. This work provides useful guidelines for designing robust visible light responsive photoreduction CO2 catalysts on the atomic scale.