Efficient Charge and Proton Balance Enabled by a 2D/2D S‐Scheme Heterojunction with a Nanochamber Design for Better Synergy of Photocatalytic CO₂ Methanation and Benzylamine Oxidation

Abstract Light‐driven CO₂ reduction integrated with benzylamine (BA) oxidation provides a promising means for achieving sustainable development, whereas whose effectiveness is challenged by imbalanced charge transfer/utilization and proton supply/consumption. To conquer these issues, herein, a 2D/2D inorganic/organic S‐scheme heterojunction is reported with a nanochamber design, featuring large‐area interfacial contact between the components for carrier transfers and sufficient exposure of spatially separated redox sites for surface reactions. Remarkably, the designed BiOI@hollow zinc‐porphyrin conjugated polymer (ZnPCP) catalyst delivers a high CH₄ yield of 577.1 µmol g_cat⁻¹ h⁻¹ and a stoichiometric N‐benzylidenebenzylamine (BDA) output of 2300.3 µmol g_cat⁻¹ h⁻¹, with both selectivities exceeding 96%. Zn coordination to porphyrin not only amplifies the internal electric field of the heterojunction and induces an intramolecular polarization electric field within ZnPCP, but also facilitates CO₂ adsorption/activation and lowers the energy barriers for CO₂ methanation, improving the charge transfer/separation dynamics and regulating the reduction reaction kinetics. Moreover, hollow chambers increase the photon and charge utilization, and coordinate the proton release and consumption, encouraging the dehydrogenation C─N coupling of BA to BDA, while simultaneously discouraging the hydrogenation of BDA to secondary amines. This study emphasizes the significance of attaining charge and proton equilibrium, providing a fresh avenue for enhancing the efficiency of photoredox catalysis.