Facile Fabrication of Ultrathin Tungsten-MFI Zeolite Films with Enhanced Hydrophobicity

Ultrathin and highly b-oriented tungsten-MFI (W-MFI) films are successfully synthesized by secondary growth in alkaline media. The effect of W species on the film formation is investigated. The synthesized films are characterized by using scanning electron microscopy, atomic force microscopy, X-ray diffraction, diffuse reflectance UV/Vis, Fourier transform infrared spectroscopy, and contact angle measurements. It has been demonstrated that the synthesized W-MFI films with a thickness of ca. 320 nm are smooth and highly b-oriented with a tiny roughness. The incorporation of W onto the framework of MFI zeolites could promote in-plane growth and whittle framework defects during secondary growth. The W-MFI films with a smooth outer surface exhibit a much higher water contact angle of 128.2° over the Si-MFI films synthesized either in alkaline media or in fluoride-containing neutral media, leading to significantly enhanced hydrophobicity on the film surface. The W-MFI film free of silanol would have broad pers...