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.