Cation sites in ETS-10:: 23Na 3Q MAS NMR and lattice energy minimisation calculations

Second-order quadrupolar broadening has rendered the study of cation sites in microporous materials almost impossible until the recent advent of the 2D multiple-quantum NMR experiment. In conjunction with computer lattice-energy-minimisation calculations we employ this powerful new technique to study the complex microporous titanosilicate ETS-10 and titanium aluminosilicate ETAS-10 systems. Evidence is presented for five unique cation sites differing greatly in their behaviour towards dehydration. Strong evidence is also given for preferential potassium cation siting.