Light harvesting engineering of covalent organic frameworks for photocatalysis

As the primary and critical step in photocatalysis, the light-harvesting capability of photocatalyst directly determines the quantity of photogenerated charge carriers. This fundamental process ultimately governs both the photocatalytic efficiency and overall solar energy conversion. Covalent organic frameworks (COFs), as a representative class of porous organic photocatalysts, demonstrate significant potential for various photocatalytic applications with the flexible structural design. In this regard, the fundamental principles and critical factors influencing light harvesting in COF photocatalysts are reviewed in this work to provide a mechanistic understanding of light absorption and utilization. Additionally, strategies for expanding the light absorption range based on the recent advancements are summarized, including donor-acceptor system design, heteroatom doping, planarization design, metal incorporation, heterostructure engineering, and sensitization. Finally, the challenges and opportunities for COFs are forecast, including developing new sensitization strategies, balancing photothermal and photocatalytic effects, and industrializing their synthesis and application.