Molecularly engineered porphyrin photosensitizers featuring multi-anchoring and alkoxy modifications for robust photocatalytic hydrogen production
A new generation of porphyrin-based photosensitizers (PoTA1–PoTA3) was developed for photocatalytic hydrogen evolution (PHE). Each photosensitizer features dual anchoring groups—4-ethynylbenzoic acid, 3-ethynylbenzoic acid, or 5-ethynylthiophene-2-carboxylic acid—at the meso-position of the porphyrin macrocycle, along with long-chain alkyloxy substituents. This dual-modification strategy suppresses charge recombination and reduces aggregation on TiO2 surfaces. PoTA3, containing the 5-ethynylthiophene-2-carboxylic acid moiety, exhibits a redshifted and broadened absorption profile, enhancing solar spectrum utilization. Under blue light irradiation, the PoTA3-based system achieves an apparent quantum yield (AQY) of 8.3%, an initial hydrogen evolution rate of 485 mmol g−1 h−1, and a turnover number (TON) of 27,858 in aqueous media, substantially outperforming PoTA1 and PoTA2. Under white light, PoTA1 and PoTA3 achieve AQY values of 5.5% and 6.8%, respectively, surpassing the benchmark YD2-o-C8 (AQY = 4.07%). The synergistic effects of enhanced light harvesting, minimized aggregation, and optimized HOMO/LUMO electron density distributions contribute to high efficiency and robust operational stability. These findings establish a flexible molecular engineering platform for next-generation solar-to-hydrogen conversion systems.