Molybdenum Carbide/Cobalt Composite Nanorods via a “MOFs plus MOFs” Strategy for High-Efficiency Microwave Absorption

Herein, we report the synthesis of one-dimensional (1D) molybdenum carbide/cobalt nanorods that consist of multiple components including Mo2C, Co, and C (Mo2C/Co/C) based on a "MOFs plus MOFs" strategy. The 1D Mo-metal–organic frameworks (MOFs) were first prepared through reflux condensation. Then, a zeolitic-imidazolate framework (ZIF-67) was used as the Co source to decorate 1D Mo-MOFs to form the Mo-MOFs/ZIF-67 precursor. Finally, 1D Mo2C/Co/C ternary composite nanorods were obtained through pyrolysis of Mo-MOFs/ZIF-67 under an Ar atmosphere. The combination of multiple components including dielectric Mo2C, C, and magnetic Co could not only optimize the impedance matching but also provide multiple channels to attenuate the electromagnetic (EM) waves including conductive loss, dielectric polarization, and magnetic resonance. Besides, the interface polarization formed by abundant heterointerfaces between Mo2C and Co/C was confirmed using a high-frequency structure simulator. The adding amount of Mo-MOFs and pyrolysis temperature were found to have a significant influence on the impedance matching and microwave absorption. Consequently, the optimized Mo2C/Co/C nanorods displayed the strongest reflection loss (RL) of −54.6 dB at 16.2 GHz corresponding to a thickness of 1.77 mm. The SRLmt (RL/matching thickness) was calculated to be 30.9, exceeding those of reported MOF derivates. What is more, the Mo2C/Co/C nanorods exhibited broad and tunable bandwidth covering from the whole X band (8.0–12.08 GHz) to the Ku band (12.56–18.0 GHz) by adjusting the amount of Mo-MOFs and pyrolysis temperature, revealing great potential for fields of microwave absorption.