Deep Eutectic Solvents for Efficient, Low-Temperature Atmospheric Water Harvesting

Water scarcity, projected to affect over half of the global population by 2050, demands decentralized and energy-efficient solutions. Sorption-based atmospheric water harvesting (AWH) is a promising approach, yet conventional porous adsorbents and ionic liquids require high regeneration temperatures, limiting energy efficiency. Here, we report the first demonstration of deep eutectic solvents (DESs) for AWH applications as safe and moderate-capacity liquid sorbents enabling low-temperature regeneration below 60 °C. Choline chloride (ChCl)-based formulations with methylurea or xylitol achieved a water uptake of 0.21 g g^-1 at 40% relative humidity and 25 °C. These DESs released 61%-65% of absorbed water at 45 °C and nearly dehydrated at 60 °C, outperforming ionic liquids that require ∼90 °C. Among tested systems, ChCl:methylurea exhibited the best performance for both absorption and desorption of water, and Fourier transform infrared (FTIR) analysis confirmed no solvent carryover in the recovered water. These findings establish the potential of DES for energy-efficient, continuous water harvesting systems.