Biomass Polymer-Stabilized Hygroscopic Salts in Cellulose Foams for Durable Atmospheric Water Harvesting

Atmospheric water harvesting (AWH) is a promising strategy to alleviate freshwater scarcity, with hygroscopic salts (e.g., LiCl) widely employed as active sorbents due to their high water affinity. However, practical deployment is hindered by the deliquescence of salts, which can lead to leakage, migration, and potential corrosion. Herein, we report a robust LiCl+CMC@cellulose composite foam fabricated via a scalable room-temperature impregnation-drying strategy. By introducing carboxymethyl cellulose (CMC) as a polymeric stabilizer, we effectively immobilize LiCl within the cellulose scaffold through ionic coordination, suppressing salt aggregation and leakage. Benefiting from the hierarchical porous architecture of cellulose and this salt immobilization strategy, the optimized composite (treated by 15 wt% LiCl, 0.5 wt% CMC solution) achieves a high water uptake of 3.57 ± 0.15 g at 25°C and 90% relative humidity (RH) within 24 h, corresponding to 16.04± 0.82 g g^{- 1} when normalized to pristine cellulose foam, representing a 15.4% enhancement over non-stabilized counterparts. Crucially, the composite exhibits excellent durability, retaining 82.4% of its capacity after ten water uptake-release cycles. Furthermore, a spray-coated carbon black (CB) surface layer enables rapid photothermal heating (up to 50.6°C under one sun irradiation), facilitating efficient solar-driven water release. This integrated, environmentally benign design offers a low-cost, durable platform for scalable, high-performance AWH.