Carboxylated MWCNT-induced mesoporous Fe3O4 constructs hierarchical heterointerface aerogels for ultra-high-efficiency microwave–terahertz broadband absorption

Inadequate interfacial polarization relaxation and insufficient synergy between magnetic and dielectric loss mechanisms constitute a major bottleneck impeding the advancement of wave-absorbing materials. This work proposes a carboxylated multiwall carbon nanotube (c-MWCNT) bridging strategy to construct c-MWCNT@Fe3O4–PPy@BNC composite aerogels (FCPB). Leveraging carboxyl–Fe3+ coordination and synergizing with PEG, c-MWCNT induces the formation of mesoporous Fe3O4. This strategy simultaneously enables the development of a 3D conductive network and improves interfacial compatibility with PPy@BNC, fostering the creation of continuous heterogeneous interfaces. Under microwave/terahertz irradiation, the heterogeneous interfaces prompt electron rearrangement due to differences in electrical conductivity and energy levels among components, thereby strengthening interfacial polarization. The optimal FCPB11 aerogel exhibits exceptional microwave absorption performance in the 2–18 GHz band, achieving a minimum reflection loss (RL) of −68.51 dB at 2.14 mm and an effective absorption bandwidth (EAB) of 6.97 GHz at 1.99 mm. Moreover, in the terahertz range (0.1–4.5 THz), it delivers a maximum RL of 44.2 dB and an EAB of 4.01 THz. Cole–Cole curves and DFT simulations further confirm the presence of multiple polarization relaxation processes, while CST simulations demonstrate a minimum radar cross-section of −44 dB m−2. Importantly, the aerogel maintains high microwave-absorbing performance even after exposure to acid, alkali, and high-temperature treatments. This study provides a new strategy for designing green, broadband, and high-performance microwave absorbers.