Infrared Investigation of the Acid and Basic Properties of a Sol-Gel Prepared MgF2

This Article reports the use of FTIR spectroscopy of adsorbed probe molecules for the characterization of the acidity and basicity of sol-gel prepared MgF2. The CO adsorption shows that this material possesses 3-, 4- and 5-fold coordinated unsaturated magnesium atoms on the surface. The strength of these Lewis acid sites is medium or weak, but their number is very high (5-6 sites/nm(2)). Whereas chloroform mainly adsorbs on Lewis acid sites, pyrrole adsorption reveals the presence of weak basic sites which are the first evidence of the basicity of fluorine atoms on the surface on metal fluorites. Both Lewis basic and acidic sites play it role in water adsorption, which is adsorbed on the surface at room temperature.