Dual-coupled interfaces drive defect-porosity synergy to enhance low-frequency electromagnetic wave absorption in MXene-based composites

Escalating demands for stealth protection and electromagnetic compatibility necessitate electromagnetic wave (EMW) absorbers with high-efficiency broadband attenuation and low-frequency extension, particularly under thin-layer constraints and low filler loading. We propose an integrated interface-pore design strategy for MXene-based absorbers to synchronously co-tune impedance matching and attenuation under thin-layer, low-loading constraints, by integrating dual-coupled heterointerfaces and hierarchical porosity. Specifically, an Fe/Mn bimetallic carboxylate MOF is pyrolyzed in situ to yield solid-solution nano-units embedded in defect-rich carbon. The tightly anchored FeO-MnO nanounits on the surface of delaminated MXene with hydrogen bonding and Ti-O-M (M = Fe/Mn) linkages form dual-coupled crystalline-amorphous-crystalline triphase heterointerfaces, thereby establishing interconnected hierarchical porosity and open transport pathways at nanosheet-particle contacts and within network voids. This interface-pore synergy optimizes the conductive network by maintaining intraflake continuity while tempering excessive conductivity, which broadens the impedance-matching band and strengthens incident-field coupling. Furthermore, the introduced tunable magnetic responses and abundant polarization-active sites effectively compensate for low-frequency loss. At a fixed filler loading of 5 wt%, the composite exhibits a minimum reflection loss (RL min ) of −72.2 dB at 3.38 GHz (S band), indicating excellent low-frequency attenuation. With a thickness of 1.16 mm, it provides an effective absorption bandwidth (EAB) of 4.64 GHz in the X/Ku bands. Furthermore, continuous low-frequency coverage exceeding 5.0 GHz across the S C bands is achieved by adjusting only five matching thicknesses. COMSOL multiphysics simulations demonstrate more uniform energy coupling and continuous volumetric dissipation. RCS calculations predict a main-lobe reduction of ≈ 32.5 dB for a metal-backed panel. This work proposes a transferable route to thin-layer, low-loading, broadband EMW absorption by integrating interface design with hierarchical porosity.