Oriented Zeolite ZSM-5 Thin Films with Various Si/Al Ratios Fabricated from Nanosheet Fragments

Manipulating the crystal growth of nanosheets is crucial for their effective utilization in the fabrication of functional films or membranes. Herein, b-oriented ZSM-5 thin films with various Si/Al ratios were fabricated from fragmented zeolite MFI nanosheets. Directly synthesized zeolite MFI nanosheets were fractured to improve their thicknesses and orientation uniformity and deposited on a flat substrate to yield b-oriented fragmented nanosheet coatings. Hydrothermal secondary growth, using precursor sols with different compositions, yielded well-intergrown oriented ZSM-5 thin films with thicknesses <100 nm; the grain morphologies varied distinctly with variations in the chemical compositions of the precursor sols. Additionally, the incorporation of Al species was supported by the water contact angles, revealing the decreasing hydrophilicity of the films with an increasing Si/Al ratio of the precursor sol. Despite different crystal morphologies, all the films prepared using precursor sols with a wide range of Si/Al ratios (50-200) exhibited preferred orientations without nucleation or twin-crystal formation, as confirmed via scanning electron microscopy, X-ray diffractometry, and confocal fluorescence microscopy.