Multi-scale designed Zeolitic Imidazolate Framework–derived N-doped cobalt/carbon composites with enhanced electromagnetic performance by magnetic-dielectric synergy

The pursuit of achieving wideband electromagnetic wave absorption to meet the demands in multiple fields has attracted attention in the field of electromagnetic wave absorption. Considering that the dipole moments of different scales can correspond to different polarization bands, the coupling of multi-scale loss mechanisms may help to realize the electromagnetic wave absorption in the wide band. Therefore, we fabricated N-doped Co/C composites derived from ZIF-67 through a facile wet chemistry approach and pyrolysis process. Due to the precise fabrication method and the design of the Stranski-Krastanow growth mode, the prepared N-doped Co/C composites contain abundant functional groups, magnetic particles, and cobalt quantum dots. By combining atomic-scale doping loss and mesoscopic-scale hollow structures, the Co/C composite materials achieve the coupling of multiple-scale loss mechanisms and demonstrate outstanding electromagnetic wave absorption performance: the minimum reflection loss (RL_min) value reaches −57.0 dB at 17.9 GHz when the thickness is 1.73 mm, and the effective absorption bandwidth (EABD) reaches the maximum value of 5.7 GHz when the thickness is 2 mm. To sum up, this work provides a new strategy for realizing the broadband absorption of further electromagnetic wave absorption materials.