Constructing Multi-Polarization in Metal-Organic Framework Gels for Electromagnetic Wave Absorption Via Ethanolamine Hetero-Coordination

Abstract

Metal-organic frameworks (MOFs) gels offer the potential for the tunable electromagnetic wave (EMW) absorption due to customisable MOF cross-linked networks and strongly polar liquid. It overcomes the drawbacks of traditional MOF-derived absorbers but the corresponding EMW loss mechanism is absent. Here, zeolite imidazole framework (ZIF) is used as functional unit in conjunction with ethanolamine (EtA) hetero-coordination and methanol to fabricate ZIF organogels with desired EMW absorption. The pore size of ZIF keeps permeability for EtA and methanol-barrier properties, which makes the formation of free -NH2 and associated -NH2 for EtA. The corresponding two species of dipole polarization losses dominate EMW attenuation. Furthermore, the intensity inversion of dual relaxation modes caused by the change in size of ZIF colloidal particles is used to improve EMW absorption for the first time. ZIF organogels exhibit a strong correlation between dielectric properties and metal node species/EtA coordination density/hydrogen bond, indicating that absorption properties can be accurately regulated. Me-ZnCo-1 sample demonstrates the optimal effective absorption bandwidth of 6.59 GHz at 2.19 mm. This study not only clearly elucidates EMW loss mechanism of ZIF organogel networks, but also proposes a creative design strategy for EMW-absorbing MOF gels.

Keywords: hetero-coordination, dipole polarization, Electromagnetic wave absorption, ZIF organogels