Hierarchical interface-engineered magnetic graphene‒SiCN aerogels via a stepwise confinement strategy for low-frequency and broadband microwave absorption

Heterogeneous interface engineering is key to tailoring intrinsic electromagnetic wave (EMW) attenuation. However, fully harnessing the functional benefits of these interfaces requires precise control of their architecture—a major challenge in hierarchical heterostructure design. Herein, a stepwise confinement strategy is proposed to construct hierarchical heterogeneous interfaces in situ within graphene aerogels, incorporating zeolitic imidazolate framework-67 (ZIF-67) nanoparticles and a polysilazane nanolayer embedding ZIF-67. Through synchronous thermal decomposition of magnetic metal and ceramics precursors, Co/CoO nanocrystals and an amorphous SiCN nanolayer are uniformly anchored onto the reduced graphene oxide (rGO) framework, creating hierarchically organized heterogeneous interfaces that comprise both nanoscale zero-dimensional (0D)–two-dimensional (2D) assemblies, such as ZIF-67-derived Co/CoO nanocrystals anchored on SiCN or rGO sheets, and extended 2D–2D contacts between the SiCN and rGO layers. These engineered heterointerfaces may induce an inhomogeneous spatial charge distribution, which in turn enhances interfacial polarization. Benefiting from synergistic magnetic–dielectric loss and improved impedance matching, the optimized magnetic graphene‒SiCN aerogel achieves a minimum reflection loss of −60.63 dB at a low frequency of 5.52 GHz and a broad effective absorption bandwidth of 7.89 GHz at a thickness of 2.4 mm. This work provides valuable insights into hierarchical heterostructure design and the fundamental electromagnetic response mechanisms governed by heterointerface engineering, paving the way for next-generation electromagnetic wave (EMW)-absorbing materials.