Construction of Ni/C composites with double-shell hollow porous structure toward high-efficiency microwave absorption

Designing structure at the nanoscale of materials has been proved to be an effective way to control electromagnetic parameters and optimize microwave absorption performance. For constructing lightweight microwave absorption materials, abundant studies focus on the preparation of absorbent with hollow, porous or yolk-shell structure. However, it is still a challenge to integrate multiple structures on one material by simple method. In this work, we found that the addition of citric acid in the preparation process played an extremely important role in regulating the structure of Ni-MOF, and developed one-step approach to synthesis double-shell hollow porous Ni-MOF. After the carbonization process, the Ni/C composite was obtained. The controllable morphology of Ni-MOF endowed Ni/C composite adjustable absorbing properties. Under the assistance of citric acid, the Ni/C composite with yolk-shell, porous, as well as double-shell hollow porous structure was also synthesized. The optimal reflection loss was −56.18 dB, the broadest bandwidth was 6.1 GHz at 2.2 mm for double-shell hollow porous Ni/C composite. Particularly, strong reflection loss at C band, X band, and Ku band was realized by regulating the structure of Ni/C composite. This work revealed the mechanism of microstructures regulating the absorbing properties, which could be beneficial to the further development of MOFs derived absorbent.