Molecular Insights into the Atmospheric Water Harvesting Hydrogels: A Review

Hydrogel can absorb water with a weight of thousands of times its dry weight. By using this advantage, hydrogels are applied for atmospheric water harvesting (AWH). As the molecular scale structure of hydrogels can determine the hydrophilicity, topology of polymer network, maximum bound water, and water permeability of the hydrogel, which determines the initial hydration rate, mechanical toughness and durability, the hydration capacity, and stable hydration rate. It is critical to rationally design AWH hydrogels by considering such structure-property relationships. This review starts with defining the key adsorption-desorption properties and theoretical ways to design components to achieve them and presents some distinguishing designs in detail. Finally, nanoscale and macroscale modeling and simulation methods to aid AWH hydrogel designs are described, and both types of methods connect to experimental testing to give a closed-loop design cycle for AWH hydrogels used for indoor air conditioning and clean water production, pursuing fast adsorption-desorption cycles, high energy efficiency and material durability.