Violations of L¨owenstein's rule in zeolites †

Zeolites, microporous aluminosilicates, are amongst the most widely used catalysts in the petrochemical industry. Zeolite catalytic functionality is in fl uenced by the location of tetrahedral alumina and associated counter-cations in the aluminosilicate framework, yet little is de fi nitively known about the factors that govern the framework aluminium arrangement. It is generally accepted that all zeolites obey L¨owenstein's rule of “ aluminium avoidance ” , and that – Al – O – Al – bond formation is forbidden. Here, we describe an unprecedented screening of aluminium distribution in catalytically active zeolite SSZ-13 (CHA) in both its protonated and sodium-containing forms, H-SSZ-13 and Na-SSZ-13, using density functional theory (DFT). We predict violations of L¨owenstein's rule in high and low silica H-SSZ-13 and other protonated frameworks considered in this investigation: H-LTA, H-RHO, H-ABW and H-MOR. The synthetic realisation of these zeolites could spur the development of new catalytic routes and materials, and the optimisation of existing zeolite catalysts.