Thermodynamic Stability Boundary of Hygroscopic Salt-Embedded Composite Materials for Atmospheric Water Harvesting

Hygroscopic salt-embedded composite materials (HSCMs) are promising for sorption-based atmospheric water harvesting (SAWH), because they combine the high sorption capacities of hygroscopic salts with the kinetics-enhancing properties of porous matrices. However, extensive efforts have been devoted to enhancing the efficiency of these emerging materials, while their stability has received comparatively less attention. This perspective highlights salt leakage from HSCMs as a critical challenge limiting their long-term application in SAWH. We first introduce the advantages of HSCMs in arid regions and highlight the issues of salt leakage. We further assess the potential multiscale impacts of salt leakage on materials, systems, environment, and human health. On this basis, we establish a thermodynamic stability boundary framework to estimate the leakage risk of HSCMs by comparing the equilibrium volume of the generated salt solution with the carrying capacity of the matrix. Finally, we propose design strategies to guide the development of next-generation leakage-free HSCMs for sustainable SAWH.