Polymerized Small-Molecule Acceptors with Linker Length-Dependent Photocatalytic Activity for High-Performance Solar Hydrogen Evolution

Developing organic semiconductor photocatalysts with alterable optical properties and excitonic behaviors for photocatalytic hydrogen evolution has received significant attention recently. Herein, three polymerized small-molecule acceptors (PSMAs) with different linker lengths, namely PY-1T, PY-2T and PY-3T, are designed and synthesized to construct nano-photocatalysts. In comparison with small-molecule YDT, these PSMAs exhibit broader absorption in both visible and near-infrared (NIR) light region as well as enlarged exciton diffusion length. In the meanwhile, the intramolecular charge transfer and separation in PSMAs is promoted by varying the linker length, leading to enhanced light harvesting and charge utilization. As a result, the single-component nano-photocatalyst based on PY-3T achieves an impressive average hydrogen evolution rate (HER) of 400.3 mmol h⁻¹ g⁻¹ under AM 1.5G sunlight (100 mW cm⁻²), which is ≈48 times greater than that of YDT NPs (8.3 mmol g⁻¹ h⁻¹). These results not only prove the potential that developing polymerized small-molecule acceptors with extended chain length as efficient photocatalysts, but also elucidate the importance of regulating linker length in designing high-performance photocatalysts.