Entangled Mesh Hydrogels with Macroporous Topologies via Cryogelation for Rapid Atmospheric Water Harvesting

Abstract

Abstract Sorption‐based atmospheric water harvesting (SAWH) is a promising technology to alleviate freshwater scarcity. Recently, hygroscopic salt‐hydrogel composites (HSHCs) have emerged as attractive candidates with their high water uptake, versatile designability, and scale‐up fabrication. However, achieving high‐performance SAWH applications for HSHCs has been challenging because of their sluggish kinetics, attributed to their limited mass transport properties. Herein, a universal network engineering of hydrogels using a cryogelation method is presented, significantly improving the SAWH kinetics of HSHCs. As a result of the entangled mesh confinements formed during cryogelation, a stable macroporous topology is attained and maintained within the obtained entangled‐mesh hydrogels (EMHs), leading to significantly enhanced mass transport properties compared to conventional dense hydrogels (CDHs). With it, corresponding hygroscopic EMHs (HEMHs) simultaneously exhibit faster moisture sorption and solar‐driven water desorption. Consequently, a rapid‐cycling HEMHs‐based harvester delivers a practical freshwater production of 2.85 L water kg sorbents −1 day −1 via continuous eight sorption/desorption cycles, outperforming other state‐of‐the‐art hydrogel‐based sorbents. Significantly, the generalizability of this strategy is validated by extending it to other hydrogels used in HSHCs. Overall, this work offers a new approach to efficiently address long‐standing challenges of sluggish kinetics in current HSHCs, promoting them toward the next‐generation SAWH applications.