Multilevel Structural Design and Heterointerface Engineering of a Host–Guest Binary Aerogel toward Multifunctional Broadband Microwave Absorption

The design of aerogels featuring high-performance electromagnetic wave absorption, multifunctionality, and high mechanical strength is of great interest for applications in complex and extreme environments. To satisfy the above requirements, novel multifunctional microwave absorption aerogels based on a multilevel structural design and host–guest heterointerface engineering strategy are reported herein, in which a freeze–thaw-assembled reduced graphene oxide (rGO) aerogel as a host is confined in an in-situ-generated guest, bridged polysilsesquioxane (BPSi) aerogel. The resulting host–guest rGO-BPSi aerogel achieves a minimal reflection loss of −51.2 dB with a broad effective absorption bandwidth of 8.4 GHz at a low filling ratio (6.2 wt %), which is attributed to the enhanced impedance matching of the gradient composition, various dielectric losses, and multiple scattering occurring within hierarchically porous structures. Furthermore, the excellent structural robustness and machinability, as well as the superhydrophobicity, thermal insulation, and antifreezing performance, guarantee the stable and durable microwave absorption application of the aerogel and resistance against deformation, water, humidity, and cold and hot environments. This design integrates multiple functionalities into a host–guest aerogel-in-aerogel system, providing valuable insights for the creation of advanced functional aerogels for diverse applications.