Covalent coupling induced-polarization relaxation in MXene-based terahertz absorber for realizing dual band absorption

Owing to the different electromagnetic (EM) wave dissipation mechanism, developing EM absorbing materials simultaneously compatible with both gigahertz (GHz) and terahertz (THz) bands is still a challenge while highly needed in 5G/6G communications. Here, we introduce the polarization loss into metallic Ti3C2Tx MXene by constructing the polysiloxane/Ti3C2Tx interface through a covalent chemistry strategy, followed by the directional-freezing process to obtain covalently bonded MXene based aerogel (CMXene). We find that the contribution of polarization relaxation and conduction loss are tunable by the heterogeneous interface, which largely affects impedance matching and the THz absorbing performance. As a result, the optimal CMXene dis-plays the broad effective bandwidth (0.2-1.4 THz) and high absorption (reflection loss of 27.3 dB with thickness of 2.5 mm) in THz band. Meanwhile, it possesses high microwave absorption performance. Our findings unveil the role of polarization relaxation in tuning the THz absorbing property and may pave the way for designing GHz and THz dual band absorber that is applied to the 5G/6G applications.