Multiscale Synergistic Radial‐Fin Sponges With Activated Sidewall Evaporation Unlock High‐Efficiency Solar‐Driven ZeroLiquid Discharge

ABSTRACT Interfacial solar evaporation is promising for hypersaline brine treatment, yet conventional 3D evaporators suffer from insufficiently activated sidewall evaporation and salt accumulation, preventing efficient and stable evaporation. Herein, we report a 3D open radial‐fin sponge (RFS) evaporator that addresses this bottleneck through a multiscale synergistic strategy. A superhydrophilic hierarchical porous network sustains capillary water supply and mass transport under high salinity. Meanwhile, the open radial‐fin architecture induces non‐isothermal natural convection and restructures local airflow along the extended sidewalls, enhancing sidewall vapor release and enabling a pure water evaporation rate of 7.13 kg m −2 h −1 , approximately 2.5‐fold higher than that of a cylindrical evaporator. The geometry‐regulated evaporation gradient, together with capillary transport, guides concentrated brine toward exposed fin extremities, where salts preferentially form porous outward‐growing structures rather than dense internal blockage. Consequently, the optimized RFS sustains continuous operation for over 530 h in 25 wt.% NaCl brine, achieving an average evaporation rate of 10.67 kg m −2 h −1 and a cumulative salt yield of 1577.61 kg m −2 . Efficient and stable evaporation is further demonstrated in diverse real waters. This work establishes a multiscale design strategy for efficient solar treatment of complex hypersaline and zeroliquid discharge.