General biotemplating of hierarchically ultra-vesicular microspheres for superior microwave absorption

• Hierarchically ultra-vesicular structures were constructed via the yeast template. • The high reflection loss value and broad absorption bandwidth were achieved. • The magnetic sample could act as the microwave absorption modifier. • Vesicle-induced space charge polarization was demonstrated by electron holography. The vesicular structure has elicited increasing interest in the field of lightweight microwave absorption (MA) materials. However, few methods exist to integrate both micro- and nanoscale vesicles within one nanoarchitecture. Herein, the high-yield and green biotemplate method is developed for the general synthesis of hierarchically ultra-vesicular microspheres (HUVMs), consisting of a hollow configuration and numerous multi-sized bubbles inside. HUVMs of metal oxides (SnO 2 , Co 3 O 4 , Fe 2 O 3 , and Mn 2 O 3 ), their combinations, and magnetic metals (Co and CoNi) have been successfully prepared. Their synergistic multi-sized vesicles simultaneously enhance dielectric loss capacity by space charge polarization and satisfy impedance matching by large cavities, proved by electron holography. Eventually, both the SnO2 and Co HUVMs demonstrate first-rank MA performance covering almost the whole bandwidth from 2 to 18 GHz with ultrahigh absorption intensity beyond –40.0 dB. These achievements provide a new avenue for precise manipulation of ultra-porous structure and foreshadow an important direction of lightweight absorbents.