Covalent Organic Framework Membranes with Asymmetric Wettability for Efficient Photocatalytic H₂O₂ Synthesis

Photocatalytic H₂O₂ synthesis from air and water is a sustainable route but hindered by mass transport and charge separation issues. Here, covalent organic framework (COF) membranes with asymmetric wettability are developed to construct triphase interfaces, locally enriching O₂ and H₂O for efficient reactions. Converting COF powders into nanostructured membranes enhances light absorption and band alignment, promoting water oxidation and charge separation. These synergistic effects boost H₂O₂ production to 52.5 mmol g^-1 h^-1 under O₂, with an apparent quantum yield 27.8 times higher than powders, and up to 148.9-fold under air. The flexible membranes can be integrated into reactors, and the in situ generated H₂O₂ enables pollutant degradation. This work demonstrates a versatile strategy for high-performance triphase photocatalysis and multifunctional membrane catalysts toward sustainable chemical synthesis.