Biomass‐Derived Bilayer Aerogels for Continuous All‐Day Atmospheric Water Harvesting: Synergistic Adsorption‐Desorption and Antimicrobial Applications

Abstract Sorption‐based atmospheric water harvesting (SAWH) provides a sustainable approach to addressing global freshwater scarcity, with significant potential for freshwater production and renewable energy utilization. However, most SAWH systems rely on hygroscopic salts, which suffer from salt leakage and agglomeration. Moreover, conventional SAWH devices operate intermittently, leading to complex processes and low energy‐time efficiency. Herein, a salt‐free, biomass‐derived bilayer aerogel, composed of chitosan, sodium alginate, and carboxymethyl cellulose, enabling continuous all‐day SAWH is presented via simultaneous adsorption‐desorption. The superhydrophilic, hierarchically porous structure with interconnected channels and a top photothermal layer achieves a high water adsorption capability of 3.97 g g ⁻¹ at relative humidity of 90% and a rapid desorption rate of 3.33 kg m ⁻² h ⁻¹ under one‐sun illumination. The feasibility of a simple prototype is demonstrated for automated and continuous SAWH under natural conditions, achieving a high water production of 3234 mL _water kg _sorbent ⁻¹ day ⁻¹ over 1 week, and outperforming previously reported SAWH systems. Moreover, the bilayer aerogel's intrinsic antibacterial properties ensure the microbial safety of the harvested water, addressing a key challenge in practical SAWH applications. This maintenance‐free design simplifies operation and provides a sustainable, off‐grid solution for freshwater production in arid and remote regions, advancing UN Sustainable Development Goal 6.