Impact of Host–Guest Interactions on the Dielectric Properties of MFM-300 Materials

Metal-organic framework (MOF) materials are attracting increasing interest in the field of electronics due to their structural diversity, intrinsic porosity, and designable host-guest interactions. Here, we report the dielectric properties of a series of robust materials, MFM-300(M) (M = Al, Sc, Cr, Fe, Ga, In), when exposed to different guest molecules. MFM-300(Fe) exhibits the most notable increase in dielectric constant to 35.3 ± 0.3 at 10 kHz upon adsorption of NH3. Structural analysis suggests that the electron delocalization induced by host-guest interactions between NH3 and the MOF host, as confirmed by neutron powder diffraction studies, leads to structural polarization, resulting in a high dielectric constant for NH3@MFM-300(Fe). This is further supported by ligand-to-metal charge-transfer transitions observed by solid-state UV/vis spectroscopy. The high detection sensitivity and stability to NH3 suggest that MFM-300(Fe) may act as a powerful dielectric-based sensor for NH3.