IT is well known that members of the montmorillonite group may be classified into a number of subgroups which differ in isomorphous substitution, having varying proportions of different cations1.

The isomorphic substitution of Al into the ITQ-22 framework was verified by 27 Al-MAS-NMR (see Methods), which shows a single resonance at 52 p.p.m., indicating that Al is tetrahedrally coordinated.