Realizing ultra-wideband absorption, desirable attenuation capability at high temperature and mechanical requirements for real-life applications remains a great challenge for microwave absorbing materials. Herein, we have constructed a porous carbon fiber/polymethacrylimide (CP) structure for acquiring promising microwave absorption performance and withstanding both elevated temperature and high strength in a low density. Given the ability of porous structure to induce desirable impedance matching and multiple reflection, the absorption bandwidth of CP composite can reach ultra-wideband absorption of 14 GHz at room temperature and even cover the whole X-band at 473 K. Additionally, the presence of imide ring group in polymethacrylimide and hard bubble wall endows the composite with excellent heat and compressive behaviors. Besides, the lightweight of the CP composite with a density of only 110 mg cm−3 coupled with high compressive strength of 1.05 MPa even at 453 K also satisfies the requirements in engineering applications. Compared with soft and compressible aerogel materials, we envision that the rigid porous foam absorbing material is particularly suitable for environmental extremes.

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waves produced by electronic devices, speed up information transmission while creating a lot of pollution, providing more and more harm to human beings. Thus, the investigation on lightweight and high efficiency EM absorbing materials and devices is widely developed. However, with the emergence of new application, such as 5G electronic devices, EM absorption materials are expected to show stable and efficient performance in thermal environments. There are rarely reports about EM absorbers to meet harsh requirement of thermal environments. The investigation of highly efficient, lightweight EM absorption materials at elevated temperature is still a great challenge.Recently, 2D materials apply to EM absorbers have attracted much attention. For example, graphene have been widely applied in EM absorbing materials due to high specific surface area, light weight, and excellent polarization loss, which enhance polarization to attenuate EM waves. [1] In addition, a class of metal carbide and metal nitride materials (MXene) as a new candidate in 2D materials has been extensively used in fields of EM absorbing and electromagnetic interference (EMI) shielding due to its excellent metal-like conductivity, abundant active surface functional groups, and good machine performance. [2][3][4][5] Ti 3 C 2 T x (T x represents OH, O, or F), a typical MXene material, can be used as a potential EMI material based on high conductivity, which has EMI effectiveness of 92 dB at 45 µm. [3] The metal-like conductivity of Ti 3 C 2 T x causes interface impedance mismatch resulting in poor EM absorbing performance, though there is part of the EM wave attenuation due to polarization and conductivity loss. It is considered that combination of dielectric and magnetic loss materials for high-efficiency EM wave absorbers as an effective strategy, which not only contributes to interface impedance matching of the material and EM waves, but also broadens the EM waves absorption mechanism. [6,7] Magnetic material-carbonyl iron powder, compared with ferrites and ferroalloys such as Fe 3 O 4 , [8] FeCo, [9] has the advantage of strong magnetic loss in the gigahertz frequency band, high Curie temperature, and low cost. [10] In addition, the flake carbonyl iron (FCI) possesses high anisotropy and its magnetic permeability is further enhanced. [11] It has been proven to exhibit the potential to be broadband andThe exploration for the potential lightweight and high efficiency microwave absorbers with thermal stability is a great challenge for researchers. More importantly, the electromagnetic parameters of absorbers at elevated temperatures are seldom studied. In this work, sandwich MXene-Ti 3 C 2 T x @flake carbonyl iron (MF) composites with tunable and efficient microwave absorption at elevated temperatures are successfully fabricated by an electrostatic selfassembly method. Both the complex permittivity and permeability of the MF are strongly temperature dependent in the temperature range of 298-473 K and X band (8.2-12.4 GHz). The efficient microwave ab...