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

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.