Thermal conversion of an Fe3O4@metal–organic framework: a new method for an efficient Fe–Co/nanoporous carbon microwave absorbing material†
A novel FeCo nanoparticle embedded nanoporous carbon composite (Fe–Co/NPC) was synthesized via in situ carbonization of dehydro-ascorbic acid (DHAA) coated Fe3O4 nanoparticles encapsulated in a metal–organic framework (zeolitic imidazolate framework-67, ZIF-67). The molar ratio of Fe/Co significantly depends on the encapsulated content of Fe3O4 in ZIF-67. The composites filled with 50 wt% of the Fe–Co/NPC-2.0 samples in paraffin show a maximum reflection loss (RL) of −21.7 dB at a thickness of 1.2 mm; in addition, a broad absorption bandwidth for RL < −10 dB which covers from 12.2 to 18 GHz can be obtained, and its minimum reflection loss and bandwidth (RL values exceeding −10 dB) are far greater than those of commercial carbonyl iron powder under a very low thickness (1–1.5 mm). This study not only provides a good reference for future preparation of carbon-based lightweight microwave absorbing materials but also broadens the application of such kinds of metal–organic frameworks.