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

Abstract

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.