Hygroscopic Core−Shell Matrices via Coaxial Multi‐Material Printing for Tailored Atmospheric Water Sorption

Sorption‐based atmospheric water harvesting (AWH) is an emerging technology for clean water production, humidity management and passive cooling. Development of salt‐embedded porous sorbents has garnered growing interest. However, hygroscopic aerogels and hydrogels as three‐dimensional (3D) scaffolds frequently lack precise control over pore morphologies, and none of the conventional hygroscopic materials is inherently printable, constraining the ability to further engineer performance‐enhancing strategies and customizable AWH applications. Herein, 3D hygroscopic core−shell matrices are developed via coaxial multi‐material printing. Tailored core−shell ink formulations broaden the compatibility of hygroscopic materials with 3D printing, enabling precise spatial integration and high shape fidelity. Each printed filament contains a LiCl‐stabilizing core encapsulated within a hierarchically porous shell, forming a Janus‐like structure with controlled compositional and structural heterogeneity. This filament‐level heterogeneity synergistically enhances surface areas, mass‐transporting pathways, salt retention and solution absorption across the whole matrices. The core−shell matrices attain high water uptake of 2.15 g g −1 under 90% RH, rapid water release under mild heating, and negligible performance degradation and structural deformation over 50 hydration−dehydration cycles — outperforming single‐material printed counterparts. Our work demonstrates, for the first time, the use of coaxial 3D printing to create structurally heterogeneous hygroscopic materials tailored for user‐defined AWH and built‐in thermal‐regulation systems.