Morphology-engineered copper-based MOF-199@MWCNTs hybrids for enhanced microwave absorption

Metal–organic frameworks (MOFs) of MOF-199 with three distinct morphologies—cubic (hexahedral)-A, octahedral-B and tetradecahedral-C—were prepared by solvothermal method via adjusting the amount of coordination modulator of lauric acid. Meanwhile, absorbing hybrids of MOF-199@multi-walled carbon nanotubes (MWCNTs) with a three-dimensional structure were constructed via π–π stacking interactions between benzene ring π-electrons in the organic ligand of MOF-199 and π electronic of MWCNTs. Scanning electron microscopy images demonstrated that MOFs particles with three distinct morphologies were obtained, with an average particle size of approximately 2 μm. The aim of this study is to investigate the influence of MOF morphology on the absorption performance. Due to the increased number of facets and relatively abundant heterogeneous interfaces of tetradecahedral MOF-199-C, the RLmin of MOF-199-C@MWCNTs hybrids reach up to −48.16 dB, which is higher than that of cubic MOF-199-A@MWCNTs (−23.21 dB) hybrids and octahedral MOF-199-B@MWCNTs (−45.77 dB) hybrids. The results indicated that increasing the number of facets promotes multiple scattering and internal reflection of electromagnetic waves, which increases the heterogeneous interfaces and promotes absorption performance.