Novel Passive Adsorption‐Based Double‐Network Composite Hydrogel for Atmospheric Water Harvesting

Freshwater scarcity has become a critical global issue, driving growing attention toward atmospheric water harvesting (AWH) technologies for their energy efficiency and sustainability. In this work, novel adsorption-based double-network composite hydrogel is successfully prepared through solution blending-freeze molding-vacuum freeze-drying approach. Using cross-linked network of polyvinyl alcohol (PVA) and hydroxypropyl cellulose (HPC) as the structural matrix and super hygroscopic material (SHM) as functional filler, the hydrogel demonstrates substantially improved mechanical strength and moisture capture capability. It is found that the PVA/HPC double-network hydrogel shows 121% increase in compressive strength and 36% improvement in toughness compared to pure PVA hydrogel. Moisture capture capacity of the PVA/HPC@SHM hydrogel is 54% higher than that of the PVA/HPC hydrogel at 25°C and 80% relative humidity (RH). Even under complex and variable outdoor conditions, the PVA/HPC@SHM hydrogel maintains better moisture capture capability. These results provide the new pathway for designing efficient, energy-free, and sustainable AWH materials.