Membrane-Confined Proton Management Orchestrates Proton-Electron Transfer for Efficient Photocatalytic Hydrogen Peroxide Synthesis.

Coordinating proton and electron transport remains a central challenge in photocatalysis, particularly for H2O2 synthesis, where two-electron oxygen reduction requires synchronized proton delivery and charge transfer. Here, we report hydroxyl-functionalized three-dimensional covalent organic framework (COF) membranes that regulate proton-coupled electron transfer within ordered nanochannels. Phenolic hydroxyl groups are precisely embedded in the membrane pores as internal proton reservoirs, while the continuous COF framework provides pathways for photogenerated electron transport. By tuning hydroxyl density, the dihydroxylated COF-2OH membrane establishes an optimal proton-management microenvironment, promoting O2 adsorption, charge separation, superoxide/*OOH intermediate formation, and dynamic proton recycling. Under one-sun irradiation in pure water and ambient air, COF-2OH achieves an H2O2 production rate of 21.79 mmol g- 1 h- 1 without sacrificial agents or cocatalysts, greatly outperforming the corresponding powder catalyst. Mechanistic experiments and simulations reveal that membrane confinement and hydroxyl-mediated proton buffering jointly synchronize proton and electron fluxes during continuous photocatalysis. The free-standing membrane can also be integrated into a tubular Al2O3-supported reactor for in situ H2O2-driven photo-Fenton degradation of organic pollutants. This work establishes proton-managing COF membranes as programmable reaction interfaces for efficient solar H2O2 production and integrated water treatment.