Molecular Engineering of Conjugated Polybenzothiadiazoles for Enhanced Hydrogen Production by Photosynthesis

The search for metal‐free organic photocatalysts for H 2 production from water using visible light remains a key challenge. Reported herein is a molecular structural design of pure organic photocatalysts, derived from conjugated polybenzothiadiazoles, for photocatalytic H 2 evolution using visible light. By alternating the substitution position of the electron‐withdrawing benzothiadizole unit on the phenyl unit as a comonomer, various polymers with either one‐ or three‐dimensional structures were synthesized and the effect of the molecular structure on their catalytic activity was investigated. Photocatalytic H 2 evolution efficiencies up to 116 μmol h −1 were observed by employing the linear polymer based on a phenyl‐benzothiadiazole alternating main chain, with an apparent quantum yield (AQY) of 4.01 % at 420 nm using triethanolamine as the sacrificial agent.