Amino Acid-Based Thermoresponsive Hydrogel/MOF Composite for Enhanced Atmospheric Water Harvesting and Solar Desalination

Abstract

Sorption-assisted atmospheric water harvesting (SAWH) is a promising strategy to mitigate the worldwide upsurge in freshwater demand. To empower the sustainable approach, suitable sorbent materials such as hydrogels, metal–organic frameworks (MOFs) and their composite structures have gained significant attention at the advent of their unique surface features like tunable porosity, high surface area, stimuli-responsiveness, and absorption desorption channels through functional sites. Delving into challenges associated with SAWH, we have presented a composite sorbent material consisting of alanine amino acid-based hydrogel and Al MOF. Stressing upon the fine-tuning of two individual sorbents, we designed several hydrogel-MOF composites and optimized the concentration of Al-MOF with 7.5 wt % of 0.5AHN with the best water uptake, moisture sorption, and desalination efficiency. The synergistic combination of inherently zwitterionic amino acid-based hydrogels with MOF opened up extended water uptake channels for the overall composite. As a result of such irreversible interaction, 0.5AHN_AlM(7.5) exhibited the highest sorption capacity of 2.21 g g–1 at 90% RH, whereas 0.26 and 0.47 g g–1 moisture uptake was measured at humidity levels of 40% RH and 60% RH, respectively. Moreover, with an evaporation rate of 0.79 kg m–2 h–1, 3.4 g of saline water was converted into freshwater within 3.5 h of solar irradiation to demonstrate its desalination efficiency. This study aims to establish a strategic method for creating environmentally friendly and effective composite materials that can be used to enhance and automate solar-powered SAWH.