Hollowing integration engineering to construct MOF-derived carbon composites for lightweight and efficient microwave absorption materials†

Abstract

The rational and precise preparation of metal–organic framework (MOF)-derived carbon-based absorbers with a fine hollow structure and the tuning of their electromagnetic properties at low loading for synergistic optimization of impedance matching and high attenuation capacity for efficient utilization have become important challenges for lightweight electromagnetic wave absorption (EMWA). Herein, a hollow particle-assembled one-dimensional (1D) nanotube carbon matrix composite loaded with dispersed Co nanoparticles is fabricated by a two-step hollowing strategy of solvent-assisted ligand exchange (SALE) and a protected etching process, combined with a subsequently optimized pyrolysis. This novel hollow structure promotes multiple reflections and scattering of incident electromagnetic waves, optimizes impedance matching, and also greatly enhances the synergistic effect of multiple loss mechanisms, remarkably improving the electromagnetic characteristics. The results indicate that Co-ZIF-HPT-700 achieves a minimum reflection loss (RL_min) of −76.93 dB at 8.96 GHz with a fill rate of only 10 wt%. At the matched thicknesses of 2.12 and 2.96 mm, it realizes full-band absorption in Ku and X bands, respectively. This work provides novel ideas for the design of a new generation of ultra-lightweight EMWA materials.