Design of zeolite by inverse sigma transformation

Although the search for new zeolites has traditionally been based on trial and error, more rational methods are now available. The theoretical concept of inverse sigma transformation of a zeolite framework to generate a new structure by removal of a layer of framework atoms and contraction has for the first time been achieved experimentally. The reactivity of framework germanium atoms in strong mineral acid was exploited to selectively remove germanium-containing four-ring units from an UTL type germanosilicate zeolite. Annealing of the leached framework through calcination led to the new all-silica COK-14 zeolite with intersecting 12-and 10-membered ring channel systems. An intermediate stage of this inverse sigma transformation with dislodged germanate four-rings still residing in the pores could be demonstrated. Inverse sigma transformation involving elimination of germanium-containing structural units opens perspectives for the synthesis of many more zeolites.