Salt Confined in MIL-101(Cr)-Tailoring the Composite Sorbents for Efficient Atmospheric Water Harvesting

• Published in: ChemSusChem Vol. 16; no. 18; p. e202300520
• Main Authors: Solovyeva, Marina V, Krivosheeva, Irina V, Gordeeva, Larisa G, Khudozhitkov, Alexander E, Kolokolov, Daniil I, Stepanov, Alexander G, Ludwig, Ralf
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 22.09.2023
• Subjects: Adsorbed water; Adsorption; Arid regions; Calcium chloride; Drinking water; Energy consumption; Hydrates; Hydrogen bonding; Melt temperature; NMR spectroscopy; Saline solutions; Sorbents; Specific energy; Synergistic effect; Water supply; atmosphere; water harvesting; Adsorption; NMR spectroscopy; MIL-101(Cr)
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202300520

The adsorption method for atmospheric water harvesting (AWH) is considered as a promising heat-driven technology for potable water supply in arid regions. This research is focused on novel composite sorbents based on hygroscopic salts loaded in the pores of MIL-101(Cr) developed for AWH. The composites based on LiCl, LiBr, CaCl , and Ca(NO ) were synthesized and comprehensively studied by SEM, XRD, N adsorption, and thermogravimetric methods. We evidence that the CaCl /MIL-101(Cr) composite demonstrates a high net water uptake of 0.52-0.59 g_(H O)/g_(composite) per cycle under conditions of Saudi Arabia and the Sahara desert as the reference regions with extra-dry climate, which exceeds the appropriate values for other adsorbents. It is shown that water adsorption on the composite cannot be presented as a combination of the adsorption on the components, thus indicating a synergistic effect. A detailed characterization of water coordination, mobility, and hydrogen bonding within the confined CaCl hydrates and salt solution using solid-state H NMR spectroscopy has been performed. It is established that pore confinement promotes a prolonged transition to a dynamically melted state of the hydrated salt and a notable decrease of the melting temperature, which facilitates the molecular transport of water and causes the alteration of sorption properties of CaCl inside MIL-101 pores. Finally, the performance of AWH employing CaCl /MIL-101(Cr) was evaluated in terms of the fractions of water extracted and collected, and the specific energy consumption, demonstrating its high potential for AWH.