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

Abstract 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 2, and Ca (NO 3) 2 were synthesized and comprehensively studied by SEM, XRD, N 2 adsorption, and thermogravimetric methods. We evidence that the CaCl 2 /MIL‐101 (Cr) composite demonstrates a high net water uptake of 0. 52–0. 59 g_ (H 2 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 2 hydrates and salt solution using solid‐state 2 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 2 inside MIL‐101 pores. Finally, the performance of AWH employing CaCl 2 /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.