COFs‐Based Metal‐Free Heterojunctions for Solar‐to‐Chemical Energy Conversion

Abstract Covalent organic frameworks (COFs) are a promising class of organic polymers with the merits of robust framework, ultrahigh porosity, and molecularly precise backbones, which reveals great potential for solar‐to‐chemical energy conversion in the context of mitigating energy and environmental crises. However, the photochemical activities of individual COFs are not as robust as desired, primarily due to their limited light absorption, insufficient dissociation of photogenerated excitons and readily recombined photogenerated carriers. Recently, COFs‐based metal‐free heterojunctions with synergistic effects provide a feasible route to boost the photocatalytic activity of COFs in more environmentally friendly and cost‐competitive manners. Herein, it is first systematically overview the advances in COFs‐based metal‐free heterojunctions from heterojunction types, heterointerfaces interactions, and primary design mechanisms. Then, typical COFs‐based metal‐free heterojunction photocatalysts (e.g., g‐C 3 N 4 ‐COFs, carbon materials‐COFs, polymer semiconductor‐COFs, COFs‐COFs heterojunction) are summarized. Finally, the challenges and long‐term outlooks for future advances of COFs‐based metal‐free heterojunction photocatalysts are offered from the terms of photocatalytic efficiency, yield, stability, cost and reaction mechanisms, as well as the standardized evaluation method of activities. It is anticipated that this review can deliver new insights into the fundamental and engineering of COFs‐based metal‐free heterojunctions for solar‐to‐chemical energy conversion, and further accelerate the development of this area.