Ultralow-density rigid network hydrogels enable ultrafast and stable solar water desalination

Interfacial solar vapor generation (SVG) has emerged as a promising strategy for water purification and desalination. Among SVG technologies, hydrogel-based evaporators stand out for their high energy efficiency and effective evaporation, but their performance often collapses under high irradiance due to insufficient water transport. Here we develop an ultralow-density rigid-network (ULR) hydrogel engineered for ultrafast water transport and evaporation. The ULR network maximizes water content and establishes steep osmotic-pressure gradients for rapid water supply, while the rigid, anti-shrinkage framework preserves hierarchical pores, sustaining capillary-driven flow and maintaining continuous vapor production under extreme irradiance. ULR evaporators surpass traditional hydrogels' theoretical maximum water transport rate, achieving an evaporation rate of 25.57 kg m⁻² h⁻¹ at 10 suns for 100 h. In practical trials, a low-cost module produced 138 L m⁻² day⁻¹, yielding 12.42 L day⁻¹ of potable water. This design advances hydrogel-based SVG toward robust, affordable solutions for real-world water scarcity.