Recent advances on covalent organic frameworks (COFs) as photocatalysts: different strategies for enhancing hydrogen generation

The excessive use of traditional fossil fuels has led to energy and environmental pollution problems. Solar-driven hydrogen generation has attracted much attention in recent years owing to its environmental friendliness and economic feasibility. So far, a series of photocatalysts have been advanced. Unfortunately, these photocatalysts face some issues including poor sunlight harvesting ability, weak photo-corrosion resistance, broad band gap, bad stability, inferior hydrogen evolution rate and so on. It just so happens that COFs have emerged to provide an opportunity for settling these issues. Covalent organic frameworks (COFs), a novel family of porous materials with regular porosity and tunable physicochemical structures, have been extensively explored as photocatalysts for hydrogen production. Moreover, their photocatalytic activities are highly structurally dependent. In this review, we mainly focus on the linkage chemistry and disparate strategies for boosting COF-based photocatalytic hydrogen generation performance in detail. The prospects and obstacles confronted in the development of COF-based photocatalysts and proposals to settle dilemmas are also discussed.