Tandem Proton Transfer in Carboxylated Supramolecular Polymer for Highly Efficient Overall Photosynthesis of Hydrogen...

Proton supply is as critical as O₂ activation for artificial photosynthesis of hydrogen peroxide (H₂O₂) via two-electron oxygen reduction reaction (2e^- ORR). However, proton release via water dissociation is frequently hindered because of the sluggish water oxidation reaction (WOR), extremely limiting the efficiency of photocatalytic H₂O₂ production. To tackle this challenge, carboxyl-enriched supramolecular polymer (perylene tetracarboxylic acid-PTCA) is elaborately prepared by molecular self-assembly for overall photosynthesis of H₂O₂. Interestingly, the interconversion between carboxyl as Brønsted acid and its conjugated base realizes rapid proton circulation. Through this efficient tandem proton transfer process, the spatial effect of photocatalytic reduction and oxidation reaction is greatly enhanced with reduced reaction barrier. This significantly facilitates 2e^- photocatalytic ORR to synthesize H₂O₂ and in the meanwhile promotes 4e^- photocatalytic WOR to evolve O₂. Consequently, the as-developed PTCA exhibits a remarkable H₂O₂ yield of 185.6 μM h^-1 in pure water and air atmosphere under visible light illumination. More impressively, an appreciable H₂O₂ yield of 78.6 μM h^-1 can be well maintained in an anaerobic system owing to in situ O₂ generation by 4e^- photocatalytic WOR. Our study presents a novel concept for artificial photosynthesis of H₂O₂ via constructing efficient proton transfer pathway to enable rapid proton circulation.