Tailoring Cross-Scale Structures in Dual-Transition Metal MXene Aerogels for Robust Microwave Absorption

Achieving broadband microwave absorption while maintaining a thin profile is a challenge due to the conflict of inherent impedance with attenuation. Herein, dual-transition metal ${\mathrm{TiNbCT}}_x$ /rGO/ ${\mathrm{Fe}}_3{O}_4$ aerogels featuring cross-scale structural tailoring, ranging from the nanoscale to the millimeter scale, were fabricated via freeze-drying. At the nanoscale, the solid-solution incorporation of Nb atoms introduces additional polarization loss, thereby enhancing the intrinsic attenuation capacity of the material. At the microscopic level, by leveraging the dimensional disparity between large-sheet rGO and small-sheet MXene, the porosity of the aerogel walls was regulated. Therefore, the conductive networks and abundant heterointerfaces were established, enabling the TNrF-1 to achieve an effective absorption bandwidth (EAB) of 6.24 GHz at a thickness of 2.0 mm, accompanied by a minimum reflection loss of $-51.47$  dB. Macroscopically, the aerogels were constructed into a stepped gradient structure whose parameters were optimized by a genetic algorithm. The optimized architecture reconciles the conflict between impedance and attenuation, delivering an exceptional EAB of 14.45 GHz with superior angular robustness. This cross-scale paradigm paves a feasible avenue for developing advanced electromagnetic functional materials.