Persistent semiquinone radicals enable efficient near-infrared-driven H2O2 photosynthesis

Photosynthesis of H₂O₂ under sunlight is a sustainable method; however, most developed photocatalysts utilize limited near-infrared light, which accounts for 52% of the solar spectrum. In typical near-infrared photocatalysts, excited electrons fall into low-energy sub-gap states, reducing the driving force for H₂O₂ generation. Here, a polydopamine-loaded porphyrin supramolecular photocatalyst efficiently utilizes near-infrared light for H₂O₂ production from H₂O and O₂, achieving an apparent quantum yield of 2.8% at 1020 nm. This substantial near-infrared utilization significantly boosts activity under full-spectrum irradiation, with an H₂O₂ generation rate of 3.37 mM/h and solar-to-chemical conversion efficiency of 2.2%. Persistent semiquinone radicals in polydopamine are demonstrated to enable ultrafast sub-gap electron transfer (ca. 79 fs) from porphyrin to polydopamine and facilitate near-infrared-driven •OOH radical generation, thereby accelerating H₂O₂ production. This study sheds light on the potential of near-infrared-responsive photocatalysts and offers insights into optimizing their performance for sustainable H₂O₂ synthesis.