Constructing hollow graphene nano-spheres confined in porous amorphous carbon particles for achieving full X band microwave absorption

The development of high-performance carbonaceous microwave absorbers to achieve full X band (8.2–12.4 GHz) efficient microwave absorption with lower filler loading ratio is highly desirable but remains challenging. Here, a kind of hollow graphene nano-spheres uniformly confined in porous amorphous carbon particles (HGS@PAC) are fabricated via a facile pyrolysis of bi-metal organic framework (bi-MOF). The successful construction of hollow graphene nano-spheres (HGS) by the in situ catalysis of Co in the framework of bi-MOF significantly improve the interface polarization and conductive loss of HGS@PAC, which ensures the high enough absorption intensity with lower filler loading ratio when used as microwave absorbers. The optimal HGS@PAC demonstrate excellent microwave absorption performance, achieving an effective absorption bandwidth of 4.2 GHz which covers the whole X band with 10 wt.% loading content and the minimum reflection coefficient reaches −32.43 dB at 9.19 GHz. In addition, compared with other MOF derived absorbers (such as Co/C, C/TiO₂ and CNTs/Co), the HGS@PAC exhibit broader effective absorption bandwidth and stronger absorption intensity. Therefore, this work provides a promising method for the design and synthesis of HGS uniformly confined in PAC with high-performance microwave absorption.