Ultrathin, Unsinkable, Janus‐Faced Solar–Thermal Interfacial Evaporator for High‐Throughput Seawater Distillation and Solar‐Water Production

Solar-thermal distillation offers immense and hitherto untapped potential for energy-efficient, sustainable freshwater production. However, critical limitations in material and system design continue to hinder water-evaporation rate (R_w) and specific water productivity (SWP), posing significant roadblocks for scalable and stable solar desalination. An ultrathin, porosity-tuned high internal phase emulsion polymer (polyHIPE, PH) scaffold is integrated with nanostructured hard-carbon florets (NCF) as a black-body absorber to create the thinnest interfacial evaporator, delivering best-in-class solar-thermal energy conversion (η-STC = 84%), rapid R_w (6.5 kg m^-2 h^-1), and efficient SWP of 18 L m^-2 day^-1 from seawater. The Janus-faced NCF@PH confines solar-thermal energy at the interface, which also promotes extensively convex water menisci, to deliver high R_w. The continuously interconnected 3D capillary channels within NCF@PH ensure continuous water transport, while their hydrophobic surfaces prevent salt deposition for robust long-term seawater distillation with high salt rejection (>90%). Furthermore, a system-level prototype termed SunSpring (SS) works to decouple the light-admitting, water-evaporation, and water-condensation steps to produce environmental protection agency (EPA)-standard freshwater (<10 ppm salinity) from highly saline seawater (35 000 ppm) for over ≈225 h of real-time continuous usage. It is also estimated that SS has the lowest energy (<3 W L^-1) and CO₂ (≈3 g L^-1) footprints, representing a paradigm shift in the water-energy nexus.