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

Abstract 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 CO 2 (≈3 g L −1 ) footprints, representing a paradigm shift in the water‐energy nexus.