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-C₂ 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.