Synergistic Super-Hygroscopic Composite Gel for Enhanced Atmospheric Water Harvesting and Desalination Applications.

Atmospheric water harvesting (AWH) produces freshwater by capturing moisture from air, offering a sustainable and decentralized solution to water scarcity without geographical limitations. Sorption-based vapor condensation has gained significant attention for garnering fresh drinking water. However, the development of multifunctional water sorption materials with versatile applications remains unexplored. In this work, the development of a super-hygroscopic composite gel composed of valine, 2-hydroxyethyl methacrylate, and N-isopropyl acrylamide-based thermoresponsive hydrogel (Valine-HEMA-NIPAM) with NH-MIL-53(Al) metal-organic framework and hygroscopic CaCl salt is reported. The composite leverages the synergistic hygroscopic properties of its components, achieving a water generation capacity of 4.48 g g at 25 °C at 90% humidity. The molecular level integration of the MOF's photothermal activity along with thermo-responsive PNIPAM polymer, which exhibits a reversible hydrophilic and hydrophobic phase transition, enables efficient photo-thermal responsiveness, resulting in complete water release within 30 min. The porous architecture and hygroscopic design facilitate efficient moisture capture, in situ water liquefaction, and effective water storage and release under varying weather conditions. Furthermore, the material exhibits promising desalination performance with an evaporation rate of 2.98 kg mh. This study not only addresses water scarcity but also highlights the potential for developing advanced porous composite materials for AWH and broader environmental applications.