Macroporous Zwitterionic Hydrogel Sponge With Enhanced Kinetics by In‐Situ UV Cryogelation for Efficient Water Production

ABSTRACT Sorption‐based atmospheric water harvesting has emerged as a promising solution to address global freshwater scarcity. Among various sorbents, salt‐based composite sorbent with hydrogel matrix is regarded as a viable candidate by combining the strong hygroscopicity and water retention capability. However, mass transport of hydrogel is limited by the pore‐deficient polymer network, leading to slow sorption kinetics. Here, we report an in situ UV cryogelation method to prepare hygroscopic zwitterionic hydrogel sponge with macroporous structure. Benefiting from the anti‐polyelectrolyte effect, the sorbent achieves a high salt loading, enabling substantial water uptake of 1.34 and 2.29 g g −1 under 30% and 60% RH. Moreover, it exhibits faster sorption‐desorption kinetics compared to dense hydrogel, owing to enhanced mass transport of both water vapor and liquid water. A batch‐processed operation mode with optimized cycle time is adopted to improve the water productivity. Consequently, a proof‐of‐concept solar‐driven water harvester demonstrates exceptional working performance of 1.38 L water kg sorbent −1 day −1 and 5.33 L water m −2 day −1 in outdoor experiments without any additional energy input. This work offers a promising approach for efficiently extracting water from ambient air.