Construction of Sponge‐Like Hydrogel with Tunable Porous Structure by Microbubble Engineering for High‐Yield Solar‐Driven Desalination of Brine

Abstract Although conventional polymer hydrogels show great promise for solar‐driven water evaporation and seawater desalination, their practical applications are fundamentally restricted due to their unsatisfactory water fluxes, dominated by the molecular osmotic water transport mechanism. Herein, sponge‐like hydrogels with tunable porous structures for high‐yield solar‐driven desalination of seawater and brine are constructed by engineering an architecturally optimized chitosan/carbon nanotube porous hydrogel (CCPH) via an air bubble‐templated foaming method. The porous hydrogel features a tunable macroporous structure that enables regulatable capillary‐driven water transport, while maintaining non‐swelling stability, fast vapor escape, heat localization, and reduced water vaporization enthalpy. The hydrogel with a height of 7 cm exposed in air achieves an exceptional water evaporation rate of 5.50 kg m −2 h −1 under 1‐sun irradiation because of the sufficient upward transport of water and the spontaneous gaining of surrounding environmental energy. Even for continuous solar desalination of a brine with 14 wt.% NaCl under 1‐sun irradiation for 50 h, CCPH maintains a high evaporation rate of 4.80 kg m −2 h −1 . The air bubble‐templated method provides an effective protocol for fabricating 3D sponge‐like porous hydrogel evaporators with enhanced salt‐resistance for high‐yield solar desalination at elevated evaporator heights.