Metal/N-Doped Carbon\nNanoparticles Derived from Metal–Organic\nFrameworks for Electromagnetic Wave Absorption

Abstract

Metal–organic frameworks (MOFs) have diverse structures\nand compositions, inspiring the boundless enthusiasm and creativity\nof researchers in the field of electromagnetism. The synthesis of\nMOF-derived nanomaterials for electromagnetic wave (EMW) absorption\nwith ultrathin matching thickness (below 1.6 mm) is highly desired\nand challenging. Here, we demonstrate a general synthesis strategy\nfor metal (Co, Ni, Fe)-based MOFs, which transformed into metal/metal-oxide\nnanoparticles (NPs) of being coated by nitrogen (N)-doped graphitized\ncarbon. The obtained carbon-coated NPs show excellent EMW absorption\nproperties. Specifically, Co-based MOFs are pyrolyzed into rhombic\ndodecahedrons with numerous ultrasmall Co NPs coated by N-doped carbon\n(Co-NC core–shell NPs). The synthesized Co-NC core–shell\nNPs possess a unique porous structure, abundant defects, and doped\nN heteroatoms, resulting in good magnetic loss (eddy current loss),\ndielectric loss (multiple reflections, interfacial polarization, conduction\nloss), and impedance matching. Therefore, the Co-NC core–shell\nNPs exhibit an excellent EMW absorption property with a very strong\nreflection loss of −56.5 dB at a matching thickness of only\n1.58 mm. The effective absorption bandwidth (EAB) is 4.4 GHz. In addition,\nthe EAB between 1 and 5 mm in thickness is up to 13.2 GHz, which already\nincludes all C bands and X bands, even the absolute S bands and Ku\nbands. This work provides an avenue to design high-performance EMW\nabsorption devices based on MOF-derived nanomaterials.