Covalent organic frameworks towards photocatalytic applications: Design principles, achievements, and opportunities

As a subclass of porous framework materials, covalent organic frameworks (COFs) feature permanent porosity, long-range order, and rigid backbones, and offer an important material platform for addressing the issues of global energy and environmental crisis. Along with the rapid development of physics, chemistry, materials science, engineering, as well as their collaboration, this research area has witnessed a dramatic growth proceeding to wide applications including gas storage and separations, energy storage and conversion devices, drug delivery, chemical sensing, and photo/electrocatalysis. Specially, structural designability, large surface area, high porosity, and superior chemical stability make COFs ideal candidates for photocatalytic systems, and great achievement and progress have been made up to now. In this Review, the key advancements made in COF-based photocatalysis are thoroughly presented. We first highlight the design principles and strategies for COFs synthesis with a special focus on their potential for photocatalysis. Following this, various photocatalytic applications of COFs are presented, covering the topics of photocatalytic hydrogen evolution, photocatalytic oxygen evolution, carbon photocatalytic dioxide reduction, photocatalytic organic transformation, and other photocatalytic reactions. Finally, the key challenges to be addressed and future avenues to be pursued are outlined, aiming to yield novel insights and contribute to game-changing innovations in this emerging area.