Abstract: With the increased electromagnetic wave (EMW) threat to military and human health, the development of EMW-absorbing materials is crucial. Metal-organic framework derivatives containing magnetic nanoparticles and a carbon matrix are potential candidates for designing efficient EMW-absorbing materials. Herein, a zeolitic imidazolate framework-67 (ZIF-67)-embedded three-dimensional melamine foam is pyrolyzed to afford carbon foam-based nitrogen-doped carbon nanotube composites, named 3D foam-like CoO/Co/N-CNTs. Magnetic CoO/Co particles are confined in the dielectric carbon nanotube skeleton. The carbon nanotubes provide considerable conductive loss, while CoO/Co magnetic particles are conducive to providing magnetic loss and adjusting impedance matching. Moreover, the numerous defect structures introduced by heteroatomic doping (nitrogen) cause dipole polarization and simultaneously adjust impedance matching. Meanwhile, the unique porous nanotube structure promotes multiple reflections and scattering of EMWs, further optimizing impedance matching. CoO/Co/N-CNTs composites exhibit a minimum reflection loss of -52.3 dB at a matching thickness of 2.0 mm, while the corresponding effective absorption bandwidth is 5.28 GHz at a matching thickness of 2.2 mm. This study reports a novel approach to fabricating a lightweight high-performance EMW-absorbing material.

Key words: Lightweight porous carbon materials, Carbon nanotubes, CoO/Co magnetic particles, Electromagnetic synergistic effect, Impedance matching