The low-dimensional units modulation of 3D floral Fe/Ni@C towards efficient microwave absorption

Metal-organic frameworks (MOF) derivatives have great potential in microwave absorption (MA) due to their customizable components, topology, and high porosity. However, the correlation between the structural parameters of the low-dimensional units and the MA performance of the 3D MOF derivatives remains unclear. Herein, we prepared a series of floral Fe/Ni@C with different petal sizes and aspect ratios to investigate the effect of low-dimensional structural parameters on the MA properties of 3D MOF derivatives. Specifically, we proposed a competitive coordination strategy. By adjusting the ratio of coordination metals, we successfully obtained floral FeNi-MOF-74 with different petal sizes and aspect ratios. Subsequently, the floral Fe/Ni@C was obtained by thermal-field modulation. It shows that, on the one hand, as the petal size increases, the conductive path is extended and the electron hopping is enhanced, thus facilitating the conductivity loss. And, with the rise of the petal aspect ratio, the tip effect is enhanced, which strengthens the polarization loss. On the other hand, the graphitization degree of the carbon components as well as the size and magnetic properties of the alloy particles can be effectively modulated by optimizing the thermal field modulation temperature. Noteworthily, under the conditions of a coordination metal ratio of 1:1 and an annealing temperature of 700 degrees C, the obtained MOF derivative exhibited excellent microwave absorption (-65.47 dB at 1.56 mm) and broadband (6.09 GHz at 1.76 mm). This strategy provides new ideas for modulating the microstructure and electromagnetic properties of MOF derivatives.