Abstract
A facile method for the preparation of microwave absorbers with low density, high microwave absorptivity, and broad band is of paramount importance to the progress in practical application. Herein, commonly-used metal organic frameworks (MOFs) prepared just by mechanical stirring in methanol at room temperature were chosen as sacrificial templates to synthesize porous carbon composites with tunable dielectric and magnetic properties. With the replacement of Co atoms on the surface of zeolitic imidazolate framework-67 (ZIF-67) by Zn atoms, a Co-doped porous carbon composite with a low-dielectric amorphous carbon/Zn shell was constructed after annealing, leading to excellent impedance matching condition. Consequently, the as-obtained composite (Co/C@C-800) shows marvelous microwave absorption properties with an absorption capacity of −43.97 dB and a corresponding effective absorption bandwidth of 4.1 GHz, far exceeding that of the traditional porous carbon and composites directly derived from ZIF-67. The results provide a convenient way to modify MOFs for enhanced microwave absorption materials from the synergy of dielectric and magnetic losses.
Highlights
To meet the ever-increasing demand for electronic communications, microprocessors, and digital systems, as well as the increasingly more severe electromagnetic pollution, extensive endeavors of scientists and engineers have been devoted to developing high-performance microwave absorbers [1,2]
In order to properly weaken the dielectric constant, a porous carbon composite with uniformly-dispersed Co nanoparticles wrapped by a low-dielectric carbon/Zn shell was successfully designed for high-performance microwave absorbers through a simple liquid method using only zinc nitrate methanol solution to generate a shell on zeolitic imidazolate framework-67 (ZIF-67)
The detailed data analysis and plenary microscopic morphology characterization demonstrated that the synergistic effect of the low-dielectric shell, internally uniformly-dispersed magnetic Co nanoparticles, high porosity, and large specific surface endows this particular composite with superior microwave absorption performance
Summary
To meet the ever-increasing demand for electronic communications, microprocessors, and digital systems, as well as the increasingly more severe electromagnetic pollution, extensive endeavors of scientists and engineers have been devoted to developing high-performance microwave absorbers [1,2]. In order to properly weaken the dielectric constant, a porous carbon composite with uniformly-dispersed Co nanoparticles wrapped by a low-dielectric carbon/Zn shell was successfully designed for high-performance microwave absorbers through a simple liquid method using only zinc nitrate methanol solution to generate a shell on ZIF-67. Benefiting from the unique evaporation of zinc metal under high pyrolysis temperature [19,20,21], as expected, a porous low-dielectric amorphous carbon/Zn shell derived from the chelation of zinc ions and 2-methylimidazole was formed to decrease the permittivity for a better impedance match. The detailed data analysis and plenary microscopic morphology characterization demonstrated that the synergistic effect of the low-dielectric shell, internally uniformly-dispersed magnetic Co nanoparticles, high porosity, and large specific surface endows this particular composite with superior microwave absorption performance
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