MOFs-Derived Hollow Co/C Microspheres with Enhanced Microwave Absorption Performance

Rational construction of a profitable microstructure in carbon-based electromagnetic composites is becoming a promising strategy to reinforce their microwave absorption performance. Herein, the microstructure design is innovatively coupled with a metal–organic frameworks (MOFs)-derived method to produce hollow Co/C microspheres (Co/C-HS). The resultant composites combine the advantages of hollow microstructures and good chemical homogeneity. It is found that the pyrolysis temperature plays an important role in determining the electromagnetic properties of these hollow Co/C microspheres, where high pyrolysis temperature will increase relative complex permittivity and decrease relative complex permeability. When the pyrolysis temperature is 600 °C, the sample (Co/C-HS-600) will show improved impedance matching and good attenuation ability, and thus an excellent microwave absorption performance with strong reflection loss (−66.5 dB at 17.6 GHz) and wide response bandwidth (over −10 dB, 3.7–18.0 GHz) can be achieved. By comparing with Co/C composites derived from conventional ZIF-67, it can be validated that a hollow microstructure is greatly helpful to upgrade the performance by boosting dielectric loss ability and suppressing a negative interaction between the carbon matrix and incident electromagnetic waves, as well as providing multiple reflection behaviors. We believe that this study may open a new avenue to promote the electromagnetic applications of MOFs-derived carbon-based composites.