Structure‐Property Relationships in Solid AlF3 Lewis Acids

Understanding the structural cause of the high Lewis acidity in the novel solid Lewis acid AlF3 is of crucial importance to tailor this important material property to the specific needs of potential applications. Based on Al and F K‐edge XAS studies, we are able to correlate high Lewis acidity with geometric distortions of the [AlF6] building blocks of AlF3. These distortions are induced by the presence of i‐OPr ligands in the AlF3−x(i‐OPr)x precursor material and can only be preserved by the application of a mild fluorinating agent like CCl2F2. High Lewis acidity is not caused by electronic modification of the aluminium atom, but by the better exposure of reactants to the acid site in the high surface area materials.