Abstract: There is limited research reported on the multiple loss mechanism of electromagnetic waves (EMW) and the development of interface models. Dielectric loss and magnetic loss, as the two primary attenuation mechanisms in EMW absorbers, still pose challenges, especially in elucidating the correlation between composition, morphology, interface, and performance. Here, we construct 3D hierarchical porous conducting network structures and Schottky heterojunctions (MoNi₄@NC-NiFe₂O₄@NC) with a high density of defects, using trimetallic NiMoFe-MOFs. Synergistic enhancement of the dielectric and magnetic losses is realized through manipulation of the defects, interfaces, phase engineering, and magnetic resonance. In particular, the even dispersion of magnetic MoNi₄ and NiFe₂O₄ nanoparticles (NPs) within the carbon matrix triggers the creation of multiple heterogeneous interfaces. These inseparable interfaces, along with oxygen vacancies, play a role in enhancing dielectric polarization, while the closely spaced interactions among magnetic units contribute to magnetic loss. After optimizing the interfacial structure, NiFe₂O₄/MoNi₄-NC exhibits remarkable EMW absorption properties. A reflection loss (R_L) value of -67.91 dB can be achieved at an ultra-thin thickness of 1.95 mm, and the effective absorption bandwidth (EAB, R_L ≤ -10 dB) is as high as 5.76 GHz. Furthermore, we conducted radar scattering cross-section (RCS) simulations using computer simulation technology (CST) software, which revealed that NiFe₂O₄/MoNi₄-NC exhibits an RCS reduction value of 39.1 dB m². Hence, this work provides comprehensive guidance for the construction of Schottky heterojunctions for lightweight EMW absorbers from a mechanistic point of view.

Key words: Trimetallic NiMoFe-MOFs, Multiple loss mechanisms, Heterogeneous interfaces, Schottky heterojunctions, Electromagnetic response