Unlocking sunlight driven photocatalysis: synthesis, diversity, and applications of COF-based S-scheme heterojunctions

Abstract

Covalent organic frameworks (COFs) are highly porous and crystalline organic polymers with remarkable thermal and chemical stability. Their tunable structures and properties have enabled their application in diverse fields. However, COFs suffer from significant drawbacks, including poor processability, strong self-stacking tendencies, limited electrical conductivity, restricted ion transport due to pore blockage, and rapid recombination of photogenerated charge carriers. To address these limitations, the construction of heterojunctions between COFs and other semiconductors has emerged as an effective approach. In particular, the S-scheme heterojunction design has recently attracted increasing attention due to its ability to suppress charge carrier recombination while preserving strong redox capability, thereby enhancing photocatalytic efficiency. Despite these advantages, there remains a scarcity of comprehensive reviews focusing on COFs-based S-scheme heterojunctions. This review provides a detailed overview of their structural characteristics and functional properties in photocatalysis. It further discusses various synthesis strategies and charge transfer mechanisms involved in constructing S-scheme heterojunctions by integrating COFs with different semiconductor materials. Additionally, the recent advancements in COFs-based S-scheme heterojunction photocatalysts are summarized, highlighting their various applications. Finally, the persisting challenges and potential future research directions in this field are critically examined.