Core-hollow cavity-shell ternary MOF-derived composites with hierarchical heterointerfaces enable ultra-broadband electromagnetic wave absorption via multiscale loss synergy

With the rapid advancement of 5G communication, radar detection, and electromagnetic stealth technologies, the integration of ultra-wideband absorption and thin matching thickness has become an inevitable requirement for electromagnetic wave (EMW) absorption materials. This study proposes a hierarchical heterointerface-hollow cavity synergy (HHS) strategy, in which stepwise coordination growth is employed to sequentially grow ZIF-8 and ZIF-67 on an MIL-125-NH₂ substrate, followed by thermal treatment to construct a core-hollow cavity-shell (CHS) structured TiO₂/C@N/C@Co/N/C (TNCC) composite. Such a unique framework achieves a minimum reflection loss (RL_min) of -64.6 dB at a thickness of 2.11 mm and an effective absorption bandwidth (EAB) of 8.05 GHz, covering the Ku band and half of the X band. The reduction in surface current density and the enhancement in volumetric loss density synergistically verify the dynamic matching-loss characteristics of TNCC. Meanwhile, at 15.025 GHz, TNCC achieves a radar cross-section (RCS) reduction of 36.3 dB and an angular coverage of 85.7 % (-180° to 180°). Multiscale characterization, finite element multiphysics simulations (COMSOL and CST), and density functional theory (DFT) calculations reveal that hollow cavity engineering enhances polarization relaxation by utilizing interfacial reflection and scattering, while effectively suppressing metal aggregation to stabilize interfacial polarization; interfacial gradient modulation facilitates efficient energy dissipation by regulating local electron coupling and magnetic loss. This work not only presents a novel strategy for the precise structural design and functional integration of MOF-derived wave-absorbing materials but also provides fundamental insights into the role of multiscale polarization and magnetic domain synergy in EMW attenuation.