Two-step polymerization for tailored donor–acceptor interactions driving efficient hydrogen evolution in visible-light photocatalysts†

Abstract

The development of materials for organic solar cells has made significant strides through the strategic combination of diverse donor structures with acceptor units in polymer backbones. In contrast, semiconducting polymers for photocatalytic hydrogen evolution have primarily focused on acceptor moieties, with limited exploration of donor contributions, primarily owing to the emphasis on designing active sites for proton reduction in inorganic catalysts. To investigate the impact of highly electron-donating moieties on photocatalytic performance, we designed and synthesized benzothiadiazole (BT)-based polymers with randomly incorporated benzodithiophene (BDT) and fluorene units via a streamlined one-pot Stille–Suzuki two-step polymerization. Comprehensive molecular characterization and optical spectroscopic analyses confirmed the successful synthesis of the target polymers. Photocatalytic hydrogen evolution studies, supported by photophysical and spectroscopic investigations, demonstrated that optimizing the proportion of BDT units in the polymer backbone enhances hydrogen evolution rates significantly. Additionally, comparative analyses further highlighted the distinct differences in the photocatalytic efficiency between the BDT and fluorene donor units, providing critical insights into their functional roles. This work underscores the potential of advancing polymer photocatalysts by fine-tuning donor–acceptor interactions through optimization of donor moiety composition, offering a robust framework for achieving superior photocatalytic performance.