SiO- defects in As-synthesized pure-silica and aluminosilicate sodalites

Abstract

The existence and distribution of Si-O- defects in pure-silica and aluminosilicate sodalites prepared from nonaqueous media containing ethylene glycol are investigated by Na-23 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.