Covalent Organic Framework‐Based Janus Membrane Photocatalysts With Extended π‐Conjugation for Continuous Photosynthesis of H ₂ O ₂ and Value‐Added Chemicals

Covalent organic framework (COF)‐based photocatalysts hold considerable promise for solar‐driven chemical transformations, yet their practical performance in conventional powder or membrane systems is often constrained by poor dispersibility, inefficient interfacial mass transport, and suboptimal charge utilization. Here, we report COF‐based Janus membrane photocatalysts with an extended π‐conjugation for continuous photosynthesis of H 2 O 2 and value‐added chemicals, in which COF structures bearing expanded conjugated side chains are uniformly immobilized on the polyacrylonitrile (PAN) substrate to create a Janus‐like interfacial architecture. This design integrates the efficient light‐harvesting and charge‐transport capabilities of the COF framework with a PAN‐induced planar interface and tunable surface hydrophobicity. As a result, the Janus COF‐membrane exhibits enhanced hydrophobicity, achieving an H 2 O 2 production rate of 7888 µmol·g −1 h −1 under visible‐light irradiation, which is 2.23 times that of the control group, alongside excellent recyclability and long‐term operational stability. Furthermore, this straightforward approach can be extended to a range of COF‐derived photocatalysts for the photosynthesis of value‐added chemicals, which demonstrate superior activity in benzylamine coupling (99% conversion and selectivity within 3 h) and Knoevenagel condensation reactions (90%–99% conversion and selectivity within an average of 6 h). Together, our findings underscore the effectiveness of interfacial microenvironment engineering in designing COF membrane‐based photocatalytic systems.