Architecture-Regulated Fe/Zr Bimetallic MOF-Derived Carbon Composites for Ultrathin and Broadband Microwave Absorption

Metal–organic framework (MOF)-derived carbon composites have emerged as promising electromagnetic wave (EMW) absorbers, yet how different precursor architectures regulate component distribution, interfacial structures, and absorption behavior remains insufficiently understood. Herein, two Fe/Zr bimetallic MOF precursors were synthesized through distinct precursor engineering strategies, namely metal-ion doping and heteroepitaxial growth, and were subsequently converted into FZC (derived from the Fe/Zr-MOF) and FOZC (derived from the Fe-MOF-on-Zr-MOF) composites by programmed pyrolysis. The doping strategy afforded a Fe/Zr-MOF precursor with a relatively homogeneous Fe and Zr distribution, whereas the epitaxial strategy produced an Fe-MOF-on-Zr-MOF precursor with a spatially organized core–shell architecture. FZC exhibited strong low-frequency absorption with a minimum reflection loss (RLmin) of −54.8 dB at 5.32 GHz with a matching thickness of 6.00 mm, while FOZC delivered superior broadband absorption at ultrathin matching thicknesses in the high-frequency region. Specifically, FOZC achieved an RLmin of −66.5 dB at 16.52 GHz with a thickness of 1.92 mm and a maximum effective absorption bandwidth of 6.5 GHz at 2.17 mm, covering 11.5–18.0 GHz. The enhanced performance of FOZC originates from its hierarchical morphology, abundant heterogeneous interfaces, balanced dielectric and magnetic losses, and optimized impedance matching. This work reveals the critical role of precursor-derived architecture in regulating EMW absorption and provides guidance for the rational design of high-performance MOF-derived absorbers.