Constructing ternary core–shell structured MWCNTs@Co/C@PANI nanocomposite for microwave absorption

Abstract The rise in electromagnetic pollution is a pressing issue, and the need for high‐efficiency microwave‐absorbing materials (MAMs) is critical in safeguarding against this growing menace. This study employs a three‐step synthesis strategy: (i) using in situ synthesis technology to grow ZIF‐67 on multi‐walled carbon nanotubes to enhance the material’s dielectric loss effect to improve microwave absorption (MA) properties. (ii) High‐temperature carbonization of ZIF‐67 in a tube furnace yields MWCNTs@Co/C magnetic composites, where graphitic carbon and Co particles synergistically optimize dielectric–magnetic coupling. (iii) The MWCNTs@Co/C@PANI ternary core–shell structure composites were coated with a polyaniline wrapping layer with moderate thickness using a common polymerization reaction, resulting in MWCNTs@Co/C@PANI ternary core–shell structural composites. The thickness of the polyaniline (PANI) coating on the surface of MWCNTs@Co/C can be modulated by changing the aniline concentration in the polymerization reaction. We systematically investigated the effects of different thickness layers of polyaniline on the MA properties of MWCNTs@Co/C and analyzed the reasons for their effects. The introduction of PANI increases heterointerfaces, enhancing interfacial polarization and optimizing impedance matching. With an optimal PANI coating thickness, the composite achieves ultra‐wide absorption bandwidth and efficient microwave absorption. The results show that when the thickness of the coaxial annular absorber made of 20 wt% MWCNTs@Co/C@PANI is just 2.5 mm, the minimum reflection loss (RLmin) is −50.6 dB, and an extremely wide effective absorption bandwidth (EAB) of 7.09 GHz can be achieved when the thickness is just 2.4 mm. In this study, conductive polymers were compounded on the surfaces of carbon materials and magnetic nanomaterials derived from MOFs to form a ternary core–shell structure, providing a novel tunable approach for the research and development of MAMs.