MOF derived NiFe@C composites with controllable multi-dimensional microstructures for broadband microwave absorption

Metal-organic framework (MOF) derivatives exhibit great potential as microwave absorbing materials (MAMs) owing to their high porosity, abundant surface sites and tunable constituents. Herein, this paper proposed an efficient microstructure controllable strategy for synthesizing thin-thickness broadband MAMs named NiFe@C by regulating its material microstructure. NiFe-MOF-74 precursors were firstly prepared through solvothermal method. By controlling the supersaturation of precursors, three kinds of microstructures were obtained: 3-dimensional lotus-like nanorods self-assembled structure, 1-dimensional nanospheres/nanorods hybrid structure, and 0-dimensional nanospheres structure. Subsequently, NiFe@C derivatives were obtained by pyrolysis, inheriting the microstructures of NiFe-MOF-74. The lotus-like structure of NiFe@C achieves an effective absorption bandwidth (reflection loss < -10 dB) of 5.09 GHz (12.91–18.00 GHz) with thickness of only 1.6 mm, while the nanospheres structure of NiFe@C exhibits the maximum absorptance of 99.96% at 17.12 GHz with thickness of 2.3 mm. This work provides a facile direction for designing thin thickness MAMs with broadband microwave absorption capability.