Hygroscopic polymer gels toward atmospheric moisture exploitations for energy management and freshwater generation

Atmospheric moisture exploitation (AME) technology has emerged as a promising alternative solution to improve the unbalanced supply-and-demand relationship between reducing essential resources (particularly energy and freshwater) and growing population. In this regard, emerging hygroscopic polymer gels (HPGs) are regarded as desirable materials for AME owing to their considerable hygroscopicity, highly tuneable structures, and easy integration with functional components. This review covers an in-depth and all-around overview of the up-to-date progress in HPGs used for AME. Firstly, the hygroscopic mechanisms of HPGs are revealed, followed by the presentation of state-of-the-art construction strategies, and the relationships between structures and properties are illustrated in detail. Furthermore, diverse cutting-edge applications based on HPGs for energy management and freshwater generation are also introduced, including fuel production, thermal dissipation, electric generation, hygrochromism, freshwater collection, and agricultural irrigation. Finally, we outline current challenges and their development trends of HPGs in AME applications in the coming future.