Atmospheric Water Harvesting Through Polymer Hydrogel Sorbents: Materials Chemistry, Design Strategies, and Applications.

The depletion of freshwater resources is a global problem threatening human health and daily chores. The limited availability of freshwater from ground or any other water body throughout the world positions atmospheric water harvesting as one of the vital alternatives. Sorption-based atmospheric water harvesting (SAWH) draws considerable attention for on-site synthesis. After moisture absorption, a hydrogel can yield water with minimal input of energy. That's how SAWH unlocks a perpetual source of clear water, which can potentially achieve the global demand for diverse uses. This review paper explores the chemistry of hygroscopic polymeric hydrogel, stimuli-responsive sorbents, structural stability, performance metrics (swelling capacity, sorption kinetics, thermodynamics), regeneration energy analysis, network design strategy, crosslinking density, the importance of co-polymerization and bio/synthetic variants. Furthermore, how a stimuli-responsive material facilitates a low-enthalpy and field-assisted uninterrupted desorption while addressing the key challenges related to salt leaching, cyclic fatigue is also a part of the discussion. The current article further highlights the present challenges related to the applicability of this on an industrial scale. This study will be concluded by highlighting futuristic opportunities for the rational engineering of energy-efficient, high-performative hydrogels for water harvesting.