Spongy hygroscopic hydrogels for efficient atmospheric water harvesting over a wide humidity range

The solar-driven adsorption atmospheric water harvesting is an emerging technology that can effectively alleviate the shortage of fresh water resources, with the characteristics of energy saving, environmental protection and economic sustainability, aligning closely with the principles of sustainable development within the framework of cleaner production. Here, this work proposes a sponge-like double-network hydrogel composite hygroscopic agent with a layered porous structure formed by mechanical foaming and in situ polymerization. The internal polymer skeleton can not only effectively prevent moisture-absorbing salt particles from aggregating and leaking, but also has stable mechanical properties. The layered porous structure and excellent superhydrophilicity enable the hydrogel hygroscopic agent to achieve excellent water absorption performance (0.785∼3.507 g g-1) over a wide range of humidity (30 %∼90 %). Thanks to the excellent photothermal performance, the hydrogel hygroscopic agent achieves a desorption efficiency of 3.82 kg m-2 h-1 under one sun. This high-performance, low-cost, and stable sponge hydrogel has great potential for large-scale atmospheric water harvesting applications, providing ideas for future multifunctional moisture-absorbing gels.