Facile synthesis of benzothiadiazole and its derivative-based covalent organic frameworks using "two-in-one" monomers for photocatalytic hydrogen generation

Photocatalytic hydrogen generation has been considered as one of the promising approaches to solve the energy and environmental crisis via using hydrogen as the green energy. In recent years, covalent organic frameworks (COFs) have received extensive attention as photocatalysts for photocatalytic hydrogen generation. However, designing and synthesizing COFs with suitable electronic structures for efficient hydrogen evolution and building the corresponding structure-property relationship still face great challenges. Herein, we rationally designed and facilely synthesized four benzothiadiazole derivative-based imine-type COFs (HIAM-0011 to HIAM-0014) using "two-in-one" monomers. The photocatalytic experiments indicate that the benzothiadiazole-based COF HIAM-0011 exhibits a much higher photocatalytic performance than the other three COFs possessing much broader light-harvesting ranges. The average hydrogen evolution rate of HIAM-0011 is up to 16.98 mmol g −1 h −1 under visible-light illumination ( λ > 420 nm) with excellent long-term and cycling stability. This work reveals that the "two-in-one" strategy is a powerful strategy to synthesize COFs with high crystallinity and provides a new guidance for the rational design of photocatalysts for efficient hydrogen generation using benzothiadiazole derivative-based organic building units. Four benzothiadiazole and its derivative-based imine-type COFs have been successfully constructed using "two-in-one" monomers for efficient photocatalytic hydrogen generation.