Interface-Synergy-Driven Core–Shell Engineering of Hierarchical Hollow Structures for Enhanced Multifunctional Low-Frequency Electromagnetic Wave Absorption and Corrosion Resistance

The advancement of next-generation communication technologies demands multifunctional materials that combine low-frequency electromagnetic wave absorption with environmental durability. In response, we propose a core–shell architecture comprising hollow silicon carbide (SiC) nanospheres uniformly assembled with a bimetallic metal–organic framework (MOF)-derived carbon matrix. Single-component SiC nanospheres struggle with low-frequency absorption due to weak polarization, no magnetic loss, and poor impedance matching. The bimetallic CoNi-MOF-derived shell can address these intrinsic limitations. The robust core–shell structure provides abundant heterointerfaces that synergistically enhance polarization, scattering, and charge transport efficiency. Moreover, dielectric-magnetic synergy optimizes impedance matching and integrates multiple loss mechanisms for maximum low-frequency absorption. Through compositional optimization, SiC@CoNi/C-3 achieves a minimum reflection loss of −64.39 dB at 5.44 GHz and a maximum effective absorption bandwidth of 5.20 GHz. Importantly, a low-frequency bandwidth of 1.76 GHz (4.80–6.56 GHz) at 4.7 mm covers the essential 5G band. Furthermore, the composites exhibit outstanding anticorrosion performance, with the most positive corrosion potential (−0.09 V vs AgCl), and the lowest corrosion current density ( I corr = 1.66 × 10 –6 A·cm –2 ), attributable to the robust physicochemical barrier imparted by the core–shell architecture. Collectively, this work establishes a pivotal design paradigm for multifunctional absorbers capable of reliable operation in low-frequency and corrosive environments.