Hydrogels and hydrogel derivatives for atmospheric water harvesting

Atmospheric water harvesting (AWH) has attracted increasing attention due to the imperative plight of water paucity in arid regions. Hence, summarizing research advances and technologies in related fields is crucial for the improvement and development of AWH. Here, we review recent progress in AWH based on hydrogel and hydrogel derivatives in view of their easy attainment, strong adaptation, and accessible popularization. We first summarize and analyze general materials, fabrication methods, mechanism and kinetics of sorption, and water harvesting procedures. Additionally, we discuss the rational design of AWH and assessments of AWH systems. Finally, we indicate future directions for hydrogel-based AWH. This review provides unique perspectives on hygroscopic composite hydrogels for AWH and presents comprehensive measurements of their efficiency and practicality. Furthermore, it gives rich guidance for further studies on water collection and simultaneously benefits analogous applications like water purification, desalination, energy harvesting, humidity sensors, and dehumidification.