Novel sol-gel prepared zinc fluoride: Synthesis, characterisation and acid-base sites analysis

The fluorolytic sol-gel route sets a milestone in the development of synthesis methods for nanoscopic fluoride materials. They exhibit fundamentally distinct properties in comparison to classically prepared metal fluorides. To broaden this area, we report in this paper the first fluorolytic sol-gel synthesis of ZnF ₂. The obtained sol was studied with dynamic light scattering (DLS). The dried ZnF ₂ xerogel was investigated with elemental analysis, thermal analysis, powder X-ray diffraction (XRD), solid-state MAS NMR, and N ₂ adsorption-desorption measurements. The characterisations revealed a remarkably high surface area of the sol-gel prepared ZnF ₂. To determine key parameters deciding its prospects in future catalytic applications, we studied the surface acidity-basicity by using in situ FTIR with different probe molecules. Compared to the previously established MgF ₂, weaker Lewis acid sites are predominant on the surface of ZnF ₂ with some base sites, indicating its potential as a heterogeneous catalyst component. In short, we believe that the successful synthesis and detailed characterisation of nanoscopic ZnF ₂ allow follow-up work exploring its applications, and will lead to studies of more metal fluorides with similar methods.