Fabrication of cage-like Ni/C@Co/NC composites for enhanced electromagnetic wave absorption performances

The research of new high-performance electromagnetic wave (EMW) absorption materials is of great significance to the solution of electromagnetic radiation pollution and the development of military stealth technology. Herein, cage-like and hierarchically porous structured Ni/C @ Co/N-doped C (Ni/C@Co/NC) composites were rationally constructed through the pyrolysis of Ni-MOF@Co-MOF precursors. By tuning the addition of Ni-MOF, Ni/C@Co/NC composites with diverse Ni/Co constitutes and structures were acquired. Compared with the Ni/C and Co/NC, all the Ni/C@Co/NC composites exhibit stronger absorption ability and broader absorption bandwidth. Among these, Ni/C@Co/NC-2 composite shows a minimum reflection loss (RL_min) of −35.90 dB at 10.45 GHz and an effective absorption band (EAB) of 6.10 GHz (11.91–18 GHz) with the thickness of 2.19 mm, Ni/C@Co/NC-4 composite exhibits a RL_min of −66.30 dB at 5.96 GHz and an EAB of 5.87 GHz (11.98–17.85 GHz) with the thickness of 2.30 mm. The excellent EMW absorption performances are ascribed to the unique hierarchically porous and cage-like structure of the composites, which makes the composites show good impedance matching characteristics and strong EMW attenuation ability. This work offers a novel strategy for constructing bimetallic core-shell MOF/MOF derived composites as high-performance EMW absorbing materials.