Benzothiadiazole and its derivative-based sp(2) carbon-conjugated covalent organic frameworks for photocatalytic hydrogen generation

Designing crystalline porous materials with efficient hydrogen evolution is a promising strategy to obtain green energy. Covalent organic frameworks have been regarded as outstanding photocatalysts for solar-to-hydrogen conversion. In particular, sp(2) carbon-conjugated covalent organic frameworks (sp(2)c-COFs), via carbon-carbon double bond linkage, have good chemical and physical stability, which has attracted great attention in recent years. Herein, we design and synthesize two series of benzothiadiazole and its derivative-based isoreticular sp(2)c-COFs (HIAM-0001 to HIAM-0006) for photocatalytic hydrogen generation. The experimental results show that benzothiadiazole-based COFs exhibit much higher photocatalytic activity compared with its derivative-based ones possessing much broader light-harvesting ranges. The average hydrogen evolution rates of HIAM-0001 and HIAM-0004 are up to 1410 & mu;mol g(-1) h(-1) and 1526 & mu;mol g(-1) h(-1) under visible-light illumination (& lambda; > 420 nm), respectively. This work presents the relevant background for the study of the structure-property relationship in benzothiadiazole and its derivative-based sp(2)c-COFs, and also provides a new guidance for the rational design and development of efficient photocatalysts for hydrogen generation.