Material characteristics and selection criteria for adsorption-based atmospheric water harvesting: An overview

Nowadays, atmospheric water harvesting (AWH) attracts great attention due to its potential to address water scarcity, especially in arid regions. A key component of adsorption-based atmospheric water harvesting is the adsorbent materials, which are porous materials characterized by high surface area and the ability to adsorb water vapor from the atmospheric air effectively. In this review article, a comprehensive overview of several adsorbent materials has been conducted, highlighting their inherent characteristics. Mainly, conventional adsorbents (silica gel and zeolite), hygroscopic salts, metal–organic frameworks, hydrogels, and composite adsorbents have been thoroughly discussed, along with their potential applications. Several AWH systems have also been presented. The review showed that the utilization of zeolite 13X under lower humidity levels is profoundly better; however, the vapor release entails elevated regeneration temperature. Moreover, MOF-801-P and MOF-841 showed appreciable performance based on material adsorption, recyclability, and water stability. Also, MCM-41 and Basolite A300 exhibited superior volumetric uptakes, notably at higher relative humidity (RH). MIL-101(Cr) has a remarkable adsorption uptake at high relative humidity. However, it is reported that MIL-101(Cr) could be used for low RH by shifting its step uptake using an internal cooling component. The review also indicated the main guidelines for selecting ideal adsorbents, highlighting the impacts of adsorption capacities, kinetics, regeneration, and climatic conditions on the proper selection of adsorbents for efficient AWH applications.