Ni-MOF/Ti₃C₂T_x derived multidimensional hierarchical Ni/TiO₂/C nanocomposites with lightweight and efficient microwave absorption

Benefiting from its large specific surface area, abundant defects and functional groups, two-dimensional (2D) laminated Ti₃C₂T_x MXene is a kind of electromagnetic wave (EMW) absorber with great potential. However, the impedance mismatch caused by the excessive conductivity, inappropriate permittivity and lack of magnetic loss seriously hinders the application of MXene to EMW absorption. Herein, multidimensional hierarchical Ni/TiO₂/C nanocomposites composed of three-dimensional (3D) hydrangea-like Ni/C microspheres and well-arranged 2D carbon sheets embedded with TiO₂ nanoparticles were successfully fabricated from a Ni-based trimellitic acid framework (Ni-BTC) and Ti₃C₂T_x MXene via facile in-situ solvothermal assembly and annealing processes. As expected, excellent EMW absorption properties were obtained only by changing the annealing temperature. The minimum reflection loss (RL_min) value of -45.6 dB and the effective absorption bandwidth (EAB) of 3.40 GHz (14.6–18.0 GHz) with a layer thickness of only 1.5 mm is obtained by annealing the sample at 700 °C. The outstanding ternary multilayer structure and the optimization of magnetoelectric synergy in impedance matching jointly create its remarkable EMW absorption performance. This work is expected to provide a simple and effective method to design MXene-based EMW absorbing materials possessing high absorption intensity, light weight, wide EAB and thin thickness.