An aluminum-rich Keggin-type structure is commonly used as a pillaring agent in clays. This complex has a composition of Al13O4(OH)24(H2O)12)7+, and is often referred to as Al13. Other compositions with the Keggin structure are possible, but they have not been as extensively studied in pillared clays. Keggin structures are of commercial interest because they are catalysts.
See pillared clay.