SiO- Defects in As-Synthesized Pure-Silica and Aluminosilicate Sodalites

The existence and distribution of Si−O - defects in pure-silica and aluminosilicate sodalites prepared from nonaqueous media containing ethylene glycol are investigated by 23 Na MAS NMR and XPS techniques. The overall results of this study demonstrate that Si−O - defects are predominantly present in the surface/near surface of pure-silica sodalite crystals and thus are not uniformly distributed. By contrast, the isomorphous substitution of Si by Al in the sodalite framework is found to produce nearly defect-free aluminosilicate sodalites.