Recyclable and Degradable Biomass-Based Water Vapor Sorbents for Efficient Atmospheric Water Harvesting

Solar-driven sorption-based atmospheric water harvesting (SAWH) is an emerging freshwater production technology for alleviating increasing water scarcity. However, existing water vapor sorbents typically suffer from environmentally unfriendly synthesis processes or components. The development of efficient SAWH sorbents that are environmentally compatible is highly demanded but remains a challenge. Herein, a novel, eco-friendly, and degradable biomass-based SAWH sorbent is developed for the solar-driven SAWH via a green approach by integrating hygroscopic choline chloride (ChCl) and photothermal polydopamine into porous alginate matrices (denoted as D-sorbent). For the first time, biomass-based ChCl is rationally chosen as the hygroscopic component, which imparts the D-sorbent with a high water vapor sorption capacity of 0.72 g g^–1 at 25 °C, 80% RH. The D-sorbent exhibits an ultralow desorption temperature of 35 °C at which ∼99% of sorbed water can be released. In addition, the D-sorbent shows highly stable water vapor sorption and solar-driven desorption performance after repeated use and recycling. More importantly, the D-sorbent is fully made of biomass resources, which can be completely degraded into nontoxic substances in the soil, avoiding the environmental burdens otherwise caused by the out-of-service sorbents.