Squaric acid-based zwitterionic covalent organic framework induces triple synergy for boosted hydrogen peroxide photosynthesis

Photocatalytic oxygen reduction reaction offers a sustainable approach for hydrogen peroxide (H₂O₂) synthesis, while the efficiency is limited by the challenge of synergistically optimizing the supply of oxygen, protons, and electrons. Here, by elaborately developing squaric acid-based zwitterionic covalent organic framework (STT COF), we propose a triple synergy strategy for boosting H₂O₂ photosynthesis. The as-prepared STT COF delivers a high H₂O₂ yield of 14356.5 μmol g^-1 h^-1 in pure water, with a notable apparent quantum yield of 40.0% at 420 nm, roughly 7.9 times that of its charge-neutral counterpart and outperforming other documented systems. Under natural sunlight irradiation, a 5 L H₂O₂ solution (~400 μM) is produced in a continuous flow membrane reactor equipped with STT COF and gas diffusion layers. Mechanism studies demonstrate that STT COF induces a strong donor-acceptor (D-A) interaction to promote electron transfer, undergoes spontaneous hydrogenation for continuous protons and facilitating oxygen uptake in a favorable configuration, collectively creating a triple synergy to boost H₂O₂ photosynthesis.