Intelligent Hygroscopic Aerogels: Moisture‐Activated Dual‐Mode Switchable Electromagnetic Response

Abstract Intelligent electromagnetic materials featuring controllable and adaptive response characteristics play a vital role in managing complex electromagnetic environments. However, effectively modulating the electromagnetic wave responses from transmission to absorption, and advancing to interference shielding through external stimuli, remains challenging. Herein, a novel moisture‐activated dual‐mode switchable electromagnetic response pattern is demonstrated in hygroscopic lithium chloride@graphene aerogel (LiCl@GA). Benefiting from the ordered hierarchical structures that accelerate vertically oriented moisture convection, the LiCl@GA exhibits ultrahigh water uptake of 4.76 g g −1 and ultrafast water sorption kinetics. This hygroscopic behavior facilitates both switchable electromagnetic wave absorption and interference shielding during water sorption‐desorption processes. The switchable functionality originates from moisture‐driven ionic conduction, where LiCl@GA absorbs ambient moisture to establish highly conductive ionic pathways. From the initial state to low water uptake (0.3 g g −1 ), the maximum change in minimum reflection loss reaches −70.03 dB. Furthermore, at high water uptake (2 g g −1 ), the LiCl@GA exhibits switchable electromagnetic interference shielding capability with a broad modulation range from 5.28 to 21.4 dB during water sorption‐desorption cycles. This study unveils previously undiscovered mechanisms for reversibly modulating electromagnetic responses in aligned porous hygroscopic aerogels, expanding their potential applications in electromagnetic interference shielding, smart sensors, and adaptive communication systems.