Mechanistic Insights into the Structural Evolution of ZIF‐67 via Electrospinning Strategy Toward High Electromagnetic Wave Absorption Performance of ZIF‐67‐Derived Carbon Nanofibers

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.