COF gel-based hygroscopic composites for high-performance solar-driven atmospheric water harvesting

Freshwater scarcity intensifies in arid/semi-arid inland regions where conventional extraction is hindered by low humidity, infrastructural limitations, and energy deficits. Sorption-based atmospheric water harvesting (SAWH) using hygroscopic salt composites (HSCs) shows promise but suffers from salt leakage at high loadings. Herein, we present here for the first time a novel class of HSCs based on covalent organic framework (COF) gels, synthesized via a one-step gelation strategy. The COF gel matrix, characterized by the rigid and open microporous-macroporous architecture without observable swelling behaviors, enables nano-confinement of lithium chloride without requiring strong ionic interactions. The resulting COF gel-based HSCs achieve stable salt loading up to 55 wt% with no observed leakage, a maximum water uptake of 3.7 kg_water kg_sorbent^-1, and a rapid water harvesting rate of 1.2 kg_water kg_sorbent^-1 h^-1. Moreover, under outdoor conditions with 60% RH, the COF gel-based HSCs achieve six solar-driven adsorption-desorption cycles per day, with a water production rate reaching 3.2 L_water kg_sorbent^-1 day^-1, demonstrating its high efficiency and potential for sustainable water collection in natural environments. This work establishes a robust strategy for salt confinement within COF networks and offers a scalable pathway toward high-performance, leakage-resistant SAWH materials.