Molecularly Functionalized Biomass Hydrogels for Sustainable Atmospheric Water Harvesting

Abstract

Atmospheric water harvesting (AWH) offers a promising pathway to alleviate global water scarcity, highlighting the need for environmentally responsible sorbent materials. In this context, this research introduces a universal strategy for transforming natural polysaccharides into effective hydrogel sorbents, demonstrated with cellulose, starch, and chitosan. The methodology unites alkylation to graft thermoresponsive groups, thereby enhancing water processability and enabling energy-efficient water release at lower temperatures, with the integration of zwitterionic groups to ensure stable and effective water sorption. The molecularly functionalized cellulose hydrogel, exemplifying our approach, shows favorable water uptake of 0.86–1.32 g g⁻¹ at 15–30% relative humidity (RH), along with efficient desorption, releasing 95% of captured water at 60 °C. Outdoor tests highlight the water production rate of up to 14.19 kg kg⁻¹ day⁻¹ by electrical heating. The proposed molecular engineering methodology, which expands the range of raw materials by leveraging abundant biomass feedstock, has the potential to advance sorbent production and scalable AWH technologies, contributing to sustainable solutions.