Zeolite films: a new synthetic approach

Abstract

Dense, adhesive zeolitic films were made for the first time by combining chemical vapour deposition (CVD) and hydrothermal methods. This new method uses a CVD process to deposit dense amorphous silica or titanium doped silica films which are then converted to a crystalline nanoporous zeolite by a hydrothermal process using an organic structure directing agent. To demonstrate the capability of the method, silicalite-1 (S-1) and titanium silicalite-1 (TS-1) zeolites were prepared. Both X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed the presence of crystalline zeolite films with well-defined morphology. Ti K-edge X-ray absorption spectroscopy (XAS) revealed the presence of the metal ions in the framework of the zeolitic matrix and in isolated, tetrahedral sites both in the amorphous and crystalline zeolite films. Both the pores and the titanium centres in the films were also shown to be accessible for molecules, by reacting with n-hexene and H₂O₂.