Molecular Synergy Engineering of Fused-Ring Polymers for Efficient Solar-Driven Hydrogen Production

The rapid recombination of photogenerated excitons in conjugated polymers constitutes a primary bottleneck for visible-light-driven photocatalytic hydrogen production. This challenge stems from the strong Coulomb binding between electrons and holes within these organic materials, which severely limits charge separation and transport. To overcome this limitation, this work presents a molecular synergy strategy through expanded fused-ring units and cyano group integration. The enlarged conjugated skeleton functions as an excited-state charge reservoir, extending carrier lifetime by providing spatial charge storage. Concurrently, cyano-derived pathways enable directional electron transfer to active sites. This synergistic design effectively suppresses nonradiative recombination and optimizes intramolecular charge distribution. The optimized polymer, TTA-sp2-CN, exhibits enhanced intrinsic dipole moment and superior charge transport capability, achieving a high hydrogen evolution rate of 23.05 mmol g–1 h–1 under visible light (λ > 420 nm) and an apparent quantum efficiency of 15.4% at 450 nm─performance that ranks among the outstanding reported for organic polymer photocatalysts. These findings establish a paradigm integrating charge reservoir construction and electron transfer modulation for designing high-performance organic photocatalysts.