Harnessing Janus-interface manipulation to convert interfacial salt accumulation into recyclable salt resources at the edges

Interfacial solar evaporation provides a sustainable pathway for freshwater production, yet it suffer critical failure in hypersaline conditions due to salt accumulation. Conventional Janus evaporators mitigate surface fouling yet fail to harvest salts as valuable resources. In this work, we introduce a wing-shaped Janus evaporator that spatially separates evaporation from crystallization through a rationally designed asymmetric interfacial force field, engineered through synergistic control of surface wettability and three-dimensional geometric inclination. This design directs brine flow to the edges for localized salt crystallization, preserving a pristine photothermal surface. The system delivers a high evaporation rate of 2.055 kg m −2  h −1 from pure water and a salt recovery rate of 69.413 g m −2  h −1 from 15 wt% brine over 120 h continuous operation. By transforming salt fouling into a resource recovery, this work establishes a paradigm shift toward zero-liquid-discharge solar desalination with dual output of freshwater and salts.