Mechanistic Insights into the Structural Evolution of ZIF‐67 via Electrospinning Strategy Toward High Electromagnetic Wave Absorption Performance of ZIF‐67‐Derived Carbon Nanofibers
Xinhui Cao, Xinyi Wu, Xue Wang, Jiamei Luo, Zhe Zhang, Yi Xue, Guoliang Zhang, Liying Zhang, Hui Zhang, Jianyong Yu
Abstract
Metal-organic framework (MOF)-derived architectures are regarded as an effective electromagnetic wave (EMW)-absorbing materials owing to their adjustable compositions and microstructures. The combination of MOFs with carbon nanofibers (CNFs) is a practical method to increase the EMW absorption ability. In this work, cobalt-based zeolitic imidazolate framework-67 (ZIF-67) serves as a self-sacrificing precursor to fabricate Co-carbon nanofiber (Co-CNF) composites via an in situ electrospinning strategy. Comparative studies on ex situ and in situ, electrospinning strategies for EMW absorption are conducted. A unique structural evolution mechanism from ZIF-67 to Co nanoparticles is explored. Numerous small Co nanoparticles are evenly distributed on the surface of in situ synthesized Co-CNF (in-Co-CNF) resulting from the collapse of the ZIF-67 framework, whereas the ZIF-67 framework remains on the surface of ex situ synthesized Co-CNF (ex-Co-CNF), encapsulating large Co nanoparticles. A lower reflection loss (RL) of -48.6 dB at 6.8 GHz with 3.5 mm is achieved for the in-Co-CNF because of the improved conduction, polarization, and magnetic losses, whereas the ex-Co-CNF only exhibits an RL of -18.3 dB at 9.3 GHz with the same thickness. A radar cross-section (RCS) simulation and a Tesla wireless transmission experiment are conducted to validate the EMW absorption of Co-CNF composites in real applications.