Abstract: Lightweight, broadband, and thermally insulating absorbers are vital for miniaturized and integrated electronics. However, conventional materials are constrained by insufficient attenuation capability, high density, and high thermal conductivity, limiting their practical application. Herein, we report the synthesis of biomass aerogels derived from pomelo peel cellulose nanosheets via an ice-templated confined self-assembly strategy. The introduction of metallic iron nanoparticles enables carbon nanotubes to grow in situ and form a continuous three-dimensional conductive network, while maintaining ultra-high porosity. This hierarchical structure significantly enhances the electrical transmission and compensates for the inherent weak dielectric loss of traditional aerogels. The embedded metal particle assembly introduces an additional loss mechanism, and the retained porosity helps to achieve ultra-low density and excellent thermal insulation performance. Therefore, aerogel shows a peak reflection loss of -63.95 dB and an ultra-wide effective absorption bandwidth of 7.44 GHz, showing excellent broadband electromagnetic absorption. In addition, it can still maintain excellent absorption performance and heat insulation performance at temperatures up to 200 °C, confirming its robust thermal stability. These findings provide a promising pathway toward the development of next-generation multifunctional absorbers for compact, thermally resilient, and reconfigurable electronic applications.

Key words: Biomass aerogel, Electromagnetic wave absorption, Thermal insulation, Ultra-light structure, Hierarchical conductive network