Nanolayered Cobalt@Carbon Hybrids Derived from Metal–Organic Frameworks for Microwave Absorption

Abstract

High-performance broadband microwave absorbers are greatly required to cope with the increasingly serious microwave radiation pollution. Integration of dielectric and magnetic components is a promising strategy to achieve desirable microwave absorption performance. Herein, we demonstrated a facile and efficient approach to fabricate two-dimensional cobalt@carbon (Co@C) hybrids by solvothermal synthesis of cobalt–metal–organic framework (Co-MOF) nanosheets and subsequent thermal pyrolysis for efficient microwave absorption application. The resultant nanolayered Co@C hybrids inherit the two-dimensional architecture of the Co-MOF nanosheets. During the thermal pyrolysis of Co-MOF, its organic component is carbonized to amorphous carbon while its cobalt ions are carbothermally reduced to cobalt nanoparticles, thus in situ integrating the magnetic metal nanocrystal with the dielectric carbon. Consequently, a wide effective absorption bandwidth of 5.44 GHz at a small thickness of 1.76 mm and a minimum reflection loss value of −49.76 dB are achieved for the wax composite with 30 wt % of Co@C hybrid pyrolyzed at 800 °C. The outstanding microwave absorption performances are attributed to the synergistic effects of the Co@C hybrid nanosheets and their large shape anisotropy, which facilitates the strong dielectric loss and good impedance matching, thus promising the nanolayered Co@C hybrid as a lightweight and high-performance microwave absorber.