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

Abstract

Herein, we report the synthesis of one-dimensional (1D) molybdenum carbide/cobalt nanorods that consist of multiple components including Mo 2 C, Co, and C (Mo 2 C/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 Mo 2 C/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 Mo 2 C, 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 Mo 2 C 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 Mo 2 C/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 SRL mt (RL/matching thickness) was calculated to be 30.9, exceeding those of reported MOF derivates. What is more, the Mo 2 C/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.

State-of-the-art in carbides/carbon composites for electromagnetic wave absorption

“…The third way usually excludes carbides with large particle size (i.e., SiC and MXene), and the mixture of MOFs/metal oxides or MOFs/polyoxometalates will be taken as the precursors, and thus it is a quite flexible route for microstructure design. 249 , 268 , 304 , 326 , 327 , 328 Ji’s group pioneered the synthesis of Mo 2 C/Co@C through the transformation of MoO 3 @ZIF-67, and optimized EM absorption performance (RL: −48.0 dB, EAB: 6.0 GHz) of final composites by the pyrolysis temperature. 304 Huang et al.…”

Heterostructured BN@Co‐C@C Endowing Polyester Composites Excellent Thermal Conductivity and Microwave Absorption at C Band

“…The cube-, dodecahedron-, and octadecahedron-like Co-C exhibited superior microwave absorption performances, with RL min reaching −52.4 dB at 10.8 GHz, −54.7 dB at 15.7 GHz, and −53.0 dB at 16.8 GHz, respectively. However, Co-C only exhibits excellent microwave absorption performances at higher frequency ranges (10-18 GHz), [39][40][41] because the specific metal coordination pattern of ZIF-67 fixes the C/Co ratio of Co-C, which makes it difficult to control the absorption bandwidths by changing dielectric loss and magnetic loss capabilities on its own. Boron nitride (BN) is a kind of thermally conductive and electrically insulating fillers with large specific surface area.…”

MoS2-Decorated Tubular Carbon Nanostructures with Enhanced Dielectric Loss for Boosting Microwave Absorption

“…In recent years, there has been a great deal of interest in the selective integration of smart components into unique one-dimensional (1D) structures . Zhao et al introduced the preparation of 1D Mo 2 C/Co/C nanorods by pyrolyzing a Mo-MOFs/ZIF-67 precursor. The Mo 2 C/Co/C nanorods exhibited excellent microwave absorption performance due to their improved impedance matching and dielectric/magnetic synergy.…”