An All-Biomass, Salt-Free Loofah Composite for Portable and Compression-Driven Atmospheric Water Harvesting

Atmospheric water harvesting (AWH) offers a promising approach to alleviating global water scarcity. However, its practical application is limited by challenges including high energy consumption, heavy reliance on sustained solar irradiation, and salt leakage from hygroscopic salts. To address these specific limitations, we develop a salt-free, loofah-based hygroscopic composite (CPGL) that enables solar-independent, low-energy water release via mechanical compression for AWH application. The three-dimensional (3D) microporous composite CPGL is fabricated by cross-linking chitosan-grafted polyamidoamine (CPG) with an interconnected loofah-fiber network. In the composite, natural loofah serves as the structural framework, biomass chitosan acts as a cross-linking bridge, and polyamidoamine dendrimers provide both high hydrophilicity and structural reinforcement. The salt-free CPGL exhibits a high moisture uptake of 1.71 g g –1 at 95% relative humidity (RH) and enables rapid water release via compression, achieving an 85.4% collection efficiency with an estimated energy requirement of only ∼1.22 kJ L –1, which is 3 orders of magnitude lower than thermal desorption. Furthermore, CPGL maintains excellent mechanical integrity, stable moisture-harvesting performance, and outstanding antibacterial activity over 50 consecutive absorption-squeezing cycles. Vacuum-packaged CPGL is portable and convenient for multiscenario application. By simultaneously eliminating salt leakage, avoiding solar dependence, and dramatically reducing energy consumption, this work provides a feasible strategy for portable, all-weather, and energy-efficient AWH using low-cost, renewable biomass resources.