Cuttlebone-Templated Fabrication of Hygroscopic Polymer Monoliths for Efficient Solar-Driven Atmospheric Water Harvesting

Hygroscopic polymer gels (HPGs) offer a promising solution for solar-driven atmospheric water harvesting (SAWH), which is adaptable to diverse climates. However, conventional HPG fabrication is often time-consuming and costly. This study presents a novel, facile, and cost-effective cuttlebone-templating approach for developing zwitterionic HPG (ZHPG) monoliths. By utilizing cuttlebone's inherent 3D porous structure as a scaffold and its CaCO₃ composition as a source of hygroscopic CaCl₂, ZHPGs with well-defined shapes, hierarchical porosity, and stable salt distribution are fabricated. These features synergistically enable excellent moisture uptake across a wide RH range, efficient solar regeneration, a mitigated salting-out effect, and superior SAWH performance. A prototype AWH device utilizing these ZHPG monoliths achieved a daily water productivity of 0.83 L_H₂O kg_ZHPG^-1 in a single cycle (under 20.3-25.0 °C and 49.2-63.7% RH) during real-world outdoor testing. This demonstrates the significant potential of the ZHPG-based SAWH for efficient water generation. Cuttlebone-templating thus provides a straightforward and economical strategy for engineering high-performance AWH sorbents, paving the way for sustainable and low-cost water harvesting.