Highlights: Metal–organic frameworks (MOFs) are used to directly initiate the gelation of graphene oxide (GO), producing MOF/rGO aerogels. The ultralight magnetic and dielectric aerogels show remarkable microwave absorption performance with ultralow filling contents. The development of a convenient methodology for synthesizing the hierarchically porous aerogels comprising metal–organic frameworks (MOFs) and graphene oxide (GO) building blocks that exhibit an ultralow density and uniformly distributed MOFs on GO sheets is important for various applications. Herein, we report a facile route for synthesizing MOF/reduced GO (rGO) aerogels based on the gelation of GO, which is directly initiated using MOF crystals. Free metal ions exposed on the surface of MIL-88A nanorods act as linkers that bind GO nanosheets to a three-dimensional porous network via metal–oxygen covalent or electrostatic interactions. The MOF/rGO-derived magnetic and dielectric aerogels Fe₃O₄@C/rGO and Ni-doped Fe₃O₄@C/rGO show notable microwave absorption (MA) performance, simultaneously achieving strong absorption and broad bandwidth at low thickness of 2.5 (− 58.1 dB and 6.48 GHz) and 2.8 mm (− 46.2 dB and 7.92 GHz) with ultralow filling contents of 0.7 and 0.6 wt%, respectively. The microwave attenuation ability of the prepared aerogels is further confirmed via a radar cross-sectional simulation, which is attributed to the synergistic effects of their hierarchically porous structures and heterointerface engineering. This work provides an effective pathway for fabricating hierarchically porous MOF/rGO hybrid aerogels and offers magnetic and dielectric aerogels for ultralight MA.

As electromagnetic absorbers with wide absorption bandwidth are highly pursued in the cutting-edge electronic and telecommunication industries, the traditional dielectric or magnetic bulky absorbers remain concerns of extending the effective absorption bandwidth. In this work, a dual-principle strategy has been proposed to make a better understanding of the impact of utilizing conductive absorption fillers coupled with implementing artificial structures design on the absorption performance. In the comparison based on the microscopic studies, the carbon nanotubes (CNTs)-based absorbers are confined to narrow operating bandwidth and relatively fixed response frequency range, which can not fulfill the ever-growing demands in the application. With subsequent macroscopic structure design based on the CNTs-based dielectric fillers, the artificial patterns show much more broadened absorption bandwidth, covering the majority of C-band, the whole X-band, and Ku-band, due to the tailored electromagnetic parameters and more reflections and scatterings. The results suggest that the combination of developing microscopic powder/bulky absorbers and macroscopic configuration design will fundamentally extend the effective operating bandwidth of microwave.

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 in situ construct hierarchical heterogeneous interfaces within graphene aerogels, incorporating ZIF-67 nanoparticles and a polysilazane nanolayer embedding ZIF-67. Through synchronous thermal decomposition of magnetic metal and ceramic precursors, Co/CoO nanocrystals and 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)–2D assemblies, such as ZIF-67-derived Co/CoO nanocrystals anchored on SiCN or rGO sheets, and extended 2D–2D contacts between SiCN and rGO layers. These engineered heterointerfaces may induce 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 EMW absorbing materials.