Facile Preparation of Polymorphic Metal–Organic Framework Nanostructures as Microwave Absorbers via One-Pot Hydrothermal Reaction

Conductive metal–organic frameworks (MOFs) have emerged as highly promising microwave absorbers, leveraging the advantage of their inherent and tunable electrical conductivity at the nanoscale. However, challenges still exist in constructing conductive MOF (c-MOF) powder materials that simultaneously possess high electron transport efficiency and excellent stability, and this issue has restricted the expansion of their applications in practical functional scenarios. To solve these issues, three M-TCNQ (M = Cu, Fe, Ni, TCNQ = tetracyanoquinone dimethane) complexes with precisely controlled nanoscale dimensions and distinct microstructures were synthesized through a one-pot hydrothermal reaction in this work. The pure Cu-TCNQ nanorods exhibited broadband microwave absorption performance, achieving an effective absorption width (EAB) of 5.3 GHz at a thickness of 2.5 mm. The minimum reflection loss (RL_min) of paraffin-based Cu-TCNQ can reach −48 dB at a thickness of 4.2 mm, and the EAB value is 5.4 GHz at 3.0 mm. Combining the density functional theory (DFT) analysis, the resistance loss between Cu–N bonds and the interfacial polarization loss of the Cu-TCNQ promotes electromagnetic loss, which is intrinsically linked to its unique nanoarchitecture that enhances charge confinement and interfacial effects. This work presents a semiconductive metal–organic complex for microwave attenuation, and more promising MAMs can be developed by utilizing a dielectric loss mechanism and designing innovative semiconductive complexes.