MXene/bimetallic CoNi-MOF derived magnetic-dielectric balanced composites with multiple heterogeneous interfaces for excellent microwave absorption

The development of high-performance microwave-absorbing materials (MAMs) to address electromagnetic (EM) pollution has become a focus of attention for researchers. The combination of MXene and heterogeneous MOF with complementary advantages can be designed into novel composites with promising microwave absorption (MWA) properties. In this paper, the M/CoNi/C series composites derived from MXene/CoNi-MOF were prepared by in situ hydrothermal-pyrolysis process. The effects of the molar ratio of Co2+/Ni2+ and the addition amount of MXene on the morphology and EM parameters of the composites were investigated, and then the MWA performance and mechanisms of M/CoNi/C composites were analyzed. The results showed that the uniformly distributed CoNi and graphitic carbon in the M/CoNi/C composites formed a core–shell structure, and TiO2 nanoparticles modified on the carbon lamellas originated from MXene. The minimum reflection loss (RLmin) value of the optimized M/Co1Ni1/C reaches −61.34 dB only at the thickness of 1.9 mm, and the effective absorption bandwidth (EAB) value is 5.2 GHz only at 1.7 mm. The RLmin values in the thickness range of 1.5–3.0 mm are all less than −30 dB. The tunable microstructures, multiple interfacial polarizations, and dielectric-magnetic synergies optimize the impedance matching, which is conducive to achieving good broadband EM wave absorption performance. This paper provides a reference strategy for the design and construction of a high-performance MXene-based microwave absorber with controllable morphology and electromagnetic parameters.