Metal/N-Doped Carbon Nanoparticles Derived from Metal-Organic Frameworks for Electromagnetic Wave Absorption

Metal-organic frameworks (MOFs) have diverse structures and compositions, inspiring the boundless enthusiasm and creativity of researchers in the field of electromagnetism. The synthesis of MOF-derived nanomaterials for electromagnetic wave (EMW) absorption with ultrathin matching thickness (below 1.6 mm) is highly desired and challenging. Here, we demonstrate a general synthesis strategy for metal (Co, Ni, Fe)-based MOFs, which transformed into metal/metal-oxide nanoparticles (NPs) of being coated by nitrogen (N)-doped graphitized carbon. The obtained carbon-coated NPs show excellent EMW absorption properties. Specifically, Co-based MOFs are pyrolyzed into rhombic dodecahedrons with numerous ultrasmall Co NPs coated by N-doped carbon (Co-NC core-shell NPs). The synthesized Co-NC core-shell NPs possess a unique porous structure, abundant defects, and doped N heteroatoms, resulting in good magnetic loss (eddy current loss), dielectric loss (multiple reflections, interfacial polarization, conduction loss), and impedance matching. Therefore, the Co-NC core-shell NPs exhibit an excellent EMW absorption property with a very strong reflection loss of -56.5 dB at a matching thickness of only 1.58 mm. The effective absorption bandwidth (EAB) is 4.4 GHz. In addition, the EAB between 1 and 5 mm in thickness is up to 13.2 GHz, which already includes all C bands and X bands, even the absolute S bands and Ku bands. This work provides an avenue to design high-performance EMW absorption devices based on MOF-derived nanomaterials.