Covalent organic framework-supported single-atom photocatalysts: site anchoring for solar H2 generation and CO2 conversion.

The development of efficient, stable, and cost-effective photocatalysts is essential for the solar-driven hydrogen evolution reaction (HER) and carbon dioxide reduction reaction (CO2RR). Conventional systems generally suffer from insufficient densities of active sites, inefficient charge separation, and poor product selectivity. In recent years, covalent organic framework-supported single-atom catalysts (COF-SACs), leveraging atomically dispersed metal centers, have not only markedly improved metal utilization but also delivered excellent charge separation efficiency and product selectivity. This review systematically outlines the core design strategies of COF-SACs from feasibility to highly efficient catalysis, with a focus on single-atom anchoring mechanisms including coordination environment regulation, functional modification, and spatial confinement/encapsulation. We then discuss how structural engineering and synergistic effects-such as donor-acceptor design, construction of molecular junctions/electron bridges, and regulation of surface crystallinity-contribute to performance optimization. The application advances of COF-SACs in the photocatalytic HER and CO2RR are summarized, highlighting mainstream systems and key strategies for their synthesis. Finally, we analyze the key challenges and offer a forward-looking perspective on opportunities for future development in photocatalytic energy conversion.