(350c) Evaluating the Role of Hygroscopic Salts on the Water Adsorption Behavior of Modified Sorbents

Water scarcity is becoming endemic, thus providing reliable methods for generating potable drinking water for remote locations remains a great, and increasingly growing, humanitarian challenge. Currently, desalination is the leading method of alternative water harvesting in arid regions, but many limitations still exist such as high operating and transportation costs, as well as the requirement to exist near seawater, limiting water access for remote and inland regions. In recent years, adsorption-based water harvesting has become an area of significant interest, in which the abundant water vapor present in the atmosphere can be extracted using porous sorbents. Metal-organic frameworks (MOFs) and silicas are porous materials that exhibit tunable surface areas and pore volumes that lend themselves to the selective removal of water vapor from air. Commonly studied sorbents that strongly adsorb water possess microporous structures, limiting their water capacity. While sorbents with larger pore geometries can theoretically hold more water, their large pore volumes often render them unstable. Recent studies have shown that hygroscopic salts can be impregnated into porous sorbents, resulting in improved water affinity, especially at low humidity. However, these salts decrease the free pore space, obstructing pore filling by water molecules. Here, we present the characterization and water adsorption behavior of salt-impregnated sorbents with a range of pore volumes, pore geometries, and surface properties to better understand how water interacts with the modified pore structure and the mechanism of pore filling that occurs. This will allow a better understanding of the use of these modified sorbents for atmospheric water harvesting applications.