Two-Dimensional Covalent-Organic Frameworks for Photocatalysis: The Critical Roles of Building Block and Linkage

Covalent organic frameworks (COFs) are a class of crystalline porous materials which contain organic build blocks linked via covalent bonds to form ordered and periodic structures. In recent years, 2D COFs have been developed as promising heterogeneous photocatalysts due to their extended pi-conjugated skeletons, high surface area, tunable structure, regular pore structure, and high crystallinity. Herein, recent advances in the design and synthesis of 2D COFs for photocatalysts are surveyed, the illustration of the structural features and synthetic strategy is focused on, and the relationship between the construction and property of 2D COFs for photocatalytic water splitting, CO2 reduction, organic transformation, and degradation of organic pollutants is elucidated. This overview is expected to provide clues to rational design and synthesis of ultra-stable, high crystalline, and high-performance 2D COFs for photocatalytic applications.