Hierarchical Microstructure Engineering of MOF-Derived Co/N-Doped Carbon Composites for Tailored Impedance Matching and Enhanced Microwave Absorption

The increasing demand for lightweight and efficient microwave absorbers has underscored the importance of simultaneously optimizing electromagnetic attenuation and impedance matching. Although MOF-derived carbon nanocomposites offer tunable conductivity and versatile microstructures, prior research has largely focused on single-structure modifications, overlooking the broader impact of microstructural configuration. In this study, we systematically engineered four distinct structural configurations, including solid, hollow, porous, and hollow-porous, within a unified ZIF-67-derived Co/N-doped carbon system. Comparative analysis reveals that hierarchical structure modulation plays a decisive role in balancing impedance matching and attenuation mechanisms. Specifically, the hollow-porous composite (HM-CoNC) achieves synergistic enhancement through multi-interface polarization, scattering, and conductive/magnetic losses, enabled by the integration of mesoporous, internal cavities, and uniformly dispersed Co nanoparticles. As a result, HM-CoNC exhibits a minimum reflection loss of -69.52   dB at 1.62   mm and an effective absorption bandwidth of 5.25   GHz at 1.69   mm, outperforming its structural counterparts. Radar cross-section simulations further validate its stealth potential with a 29.87   dB·m² reduction relative to the uncoated substrate. These findings provide valuable insight into the microstructure-performance relationship and highlight hierarchical engineering as an effective strategy for designing high-performance microwave absorbing materials.