Preparation, characterization and photoreactivity of titanium(IV) oxide encapsulated in zeolites

Abstract

The preparation, characterization and photoreactivity of titanium(IV) oxide encapsulated inside either sodium- or ammonium-exchanged zeolite Y (NaY and NH₄Y), mordenite (NaM and NH₄M) or potassium zeolite L (KL) are presented. The material was prepared by an ion-exchange method with ammonium titanyl oxalate monohydrate aqueous solution, (NH₄)₂TiO(C₂O₄)₂·H₂O. The results of X-ray photoelectron spectroscopy, chemical analysis and photolysis studies support the contention that the exchanged titanium species locate dominantly inside the zeolite cavities, and not on the external surfaces. The TiO²⁺-exchanged zeolite exhibits characteristics of TiO₂, such as photoreduction of methyl viologen to methyl viologen radical cation. A significant blue shift of the UV–VIS reflectance spectrum (onset ca. 330 nm), compared with those of bulk anatase and rutile TiO₂, and a lack of an X-ray diffraction pattern of TiO₂ in the TiO₂–zeolite samples indicate that the particle size of the TiO₂ encapsulated inside the zeolite is on the nanometre scale.