Biomass-Derived Super Hygroscopic Polymer Films for Sustainable Moisture Harvesting

Extracting ubiquitous atmospheric water is a sustainable strategy to enable decentralized access to safely managed water. Early efforts on fog capture and dewing enabled the gathering of small water droplets from air, which is only applicable to regions with high relative humidity (RH). The state-of-the-art sorbent-assisted atmospheric water harvesting presents a promising and universal approach for a wide humidity range but remains challenging due to its limited daily water output at low relative humidity (≤ 30% RH). Here, we will present our newly developed super hygroscopic polymer films (SHPFs) made from renewable biomasses consisting of konjac glucomannan (KGM) and hydroxypropyl cellulose (HPC), exhibiting excellent water uptake of 0.64 g g^-1 at 15% RH and 0.96 g g^-1 at 30% RH. KGM facilitates the highly porous structures with enlarged air-polymer interfaces for active moisture capture and water vapor transport. Thermoresponsive HPC enables phase transition of SHPFs at a low temperature to assist the release of collected water via hydrophobic interactions. With rapid sorption-desorption kinetics, SHPFs are capable of operating 14-24 cycles per day in arid environments, equivalent to a water yield of 5.8-13.3 L kg^-1. Synthesized via a simple casting method using sustainable raw materials, SHPFs highlight the potential for low-cost and scalable atmospheric water harvesting technology to mitigate the global water crisis.