Donor–acceptor type covalent organic frameworks: design, optimization strategies and applications

Covalent organic frameworks (COFs) have emerged as one of the hottest research topics in various applications due to their designed structures, adjustable pore sizes, and abundant active sites. However, the high electron-hole recombination rate and short carrier lifetime in non-donor-acceptor type COFs are inevitable issues. The electron donor-acceptor (D-A) type COFs, which are synthesized by introducing donor and acceptor units into the COF skeleton, combined with effective carrier separation, adjustable bandgap, and sensitive photoelectric response, are considered an effective strategy for improving exciton dissociation and optimizing carrier transport. In recent years, D-A type COFs have witnessed exponential expansion in applications spanning photocatalysis, energy storage, and photothermal therapy. Consequently, there exists an imperative necessity to comprehensively summarize and expound upon the challenges and prospects pertaining to the development of D-A type COFs. In this review, we first summarize the common connecting bonds as well as the building blocks for the synthesis of D-A type COFs. Several strategies for optimizing D-A type COFs and their recent progress in photocatalysis, photothermal therapy, and energy storage are then presented. Finally, we delineate the current challenges and impediments of D-A type COFs and offer a forward-looking perspective on the future development of D-A type COFs. This review is poised to encourage researchers with a more profound comprehension of the design strategies and applications of D-A type COFs, thereby inspiring them to conduct more incisive research into the challenges and developmental prospects of D-A type COFs.