Engineering Carbon Nanotube Networks in MOF-Derived Fe@NC Composites for Lightweight and Broadband Electromagnetic Wave Absorption

The in situ growth of carbon nanotubes (CNTs) on metal-organic framework (MOF)-derived carbon matrices offers a promising route for lightweight and high-performance electromagnetic wave (EMW) absorbers. However, achieving controllable CNT growth while maintaining balanced dielectric properties and impedance matching remains a major challenge. Herein, Fe-citrate is introduced as an integrated precursor that simultaneously functions as a Fe source, chelating ligand, and carbon feedstock, controlling in situ growth of CNTs without external carbon sources. During pyrolysis, in situ-formed Fe nanoparticles catalyze the formation of high-aspect-ratio CNT networks on N-doped carbon (NC) derived from zeolitic imidazolate framework-L (ZIF-L), a Zn-based MOF. By regulating the Fe-citrate content, the density and morphology of CNTs can be precisely tailored, thereby tuning the dielectric response and impedance matching characteristics of the resulting Fe@NC-CNT composites. Benefiting from the optimized balance between conductive attenuation and impedance matching, the Fe@NC-CNT composites achieve a minimum reflection loss of -60.4 dB at 12.5 wt % and a maximum effective absorption bandwidth of 7.6 GHz at 10 wt %. This work establishes a versatile strategy for engineering CNT networks in MOF-derived materials and provides insights into the structure-electromagnetic property relationship governing broadband microwave absorption.