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Synthesis of core–shell Co@S-doped carbon@ mesoporous N-doped carbon nanosheets with a hierarchically porous structure for strong electromagnetic wave absorption

Electromagnetic wave absorbents with hierarchically porous and core–shell structures have significantly positive influence on the electromagnetic wave absorption because of the enhanced interfacial polarization. Furthermore, the core–shell structure also introduces components with strong dielectric loss and good resistance to chemical corrosion. Herein, the cobalt–metal–organic frameworks @mesoporous polydopamine (Co–MOF@MPDA) composites with a core–shell structure are prepared by the bottom-up monomicelle assembly. After calcination, the Co@S-doped carbon core and mesoporous N-doped carbon shell (Co@SC@MNC) were obtained. Through adjusting the calcination temperature, the dielectric and magnetic loss can be tuned, resulting in the strong absorption capability for the electromagnetic wave. The minimum reflection loss reaches −72.3 dB, while the effective absorption bandwidth is as broad as 6.0 GHz. The unique structure and the formation of internal cavity between Co@SC and MNC contribute to the interfacial polarization. The enhancement of the dipole polarization loss and conduction loss are ascribed to the S, N-doped hierarchically porous carbon. Importantly, the presence of Co nanoparticles facilitates the magnetic–dielectric synergy to improve the impedance matching due to the introduction of magnetic loss. The novel structural design has potential application in the electromagnetic wave absorption field.