Sub-nanofluidic Photochemical Membrane with Catalytically Active Channels for Solar Ammonia Synthesis

Solar-driven conversion of N2 and H2O into ammonia under ambient conditions offers an alternative to the energy-intensive Haber–Bosch process, yet current advances are largely limited by material-focused strategies that insufficiently address coupled transport and interfacial reaction processes. Herein, we report a sub-nanofluidic photochemical membrane with catalytically active channels that integrate light harvesting, catalytic activation, and mass transport within a unified architecture for solar ammonia synthesis. The membrane consists of ZnIn2S4 atomically thin sheets and molybdenum disulfide (MoS2) quantum monolayers, forming ordered sub-nanometer channels that are intrinsically catalytic. This design establishes a confined reaction environment in which nanofluidic transport, gas–liquid interfacial regulation, and charge carrier dynamics are synergistically coupled. In particular, the combination of hydrophilic–hydrophobic interfaces and sub-nanofluidic-engineered serpentine flow pathways enhances reactant accessibility, residence time, and photon utilization, thereby overcoming diffusion and activation limitations typical of conventional photocatalytic systems. With these merits, the membrane achieves an ammonia production rate of 4.39 μg cm–2 h–1 (2.48 mmol gcat.–1 h–1) with ∼70% ammonia selectivity and maintains stable operation over 48 h of continuous testing. The achieved ammonia production rate compares favorably with those of reported photocatalytic platforms and some electrocatalytic N2 fixation systems. This work introduces a catalytically active nanofluidic channel paradigm for solar-driven N2 fixation and highlights the importance of material-transport co-engineering in bridging the gap between nanoscale catalytic design and device-level performance for chemical synthesis.