Abstract:

Metal-organic frameworks (MOFs) are considered as a novel type of microwave absorption (MA) material owing to the sufficient pore structure, diverse configurations, and easy-to-control magnetic properties. However, their evolution is limited by the imperfect impedance matching conditions caused by the undesirable microstructure. Herein, two types of novel porous coral-like carbon/Co₃O₄ and carbon/Co composites have been effectively fabricated for the first time by a facile heat treatment process of precursor Co-MOF-71. The graphitization degree, magnetic property and MA ability of the product can be effortlessly tuned by altering the heat treatment temperature of Co-MOF-71. Remarkably, S500 (Co-MOF-71 calcined at 500 °C) composite displays strong and multi-frequency absorption performance, whose minimum reflection loss (RL) value achieves -36.4 dB with an absorbing thickness of 3.0 mm and attains an effective absorbing bandwidth (RL≤-10 dB) of 5.76 GHz (almost covers whole Ku band) at a thinner coating thickness of 2.5 mm. Such superb MA ability has roots in the coral-like structure derived from the layer Co-MOF-71, sufficient electromagnetic loss. This work ameliorates the MA ability of MOFs through a special nanostructural design, which provides a fresh way for the preparation of novel MA materials.

Key words: Co-MOF-71, Coral-like structure, Ku band, Magnetoelectric synergy, Electromagnetic absorption