Real sol-gel synthesis of catalytically active aluminium fluoride

Amorphous AlF3 prepared via an anhydrous sol-gel synthesis route exhibits high surface area and Lewis acidity far beyond those known for crystalline AlF3 phases. Its catalytic properties are comparable to those of SbF5. Basis of its unusual properties is a sol-gel fluorination with anhydrous HF in organic solvents yielding first a wet Al-F-sol-gel, which can be dried and eventually post-fluorinated. All parts of the synthesis route were thoroughly investigated. The results of these investigations together with detailed analysis of the Al-F-materials obtained are reported and discussed.