Seeding-free synthesis of high-performance MFI zeolite membranes on superhydrophobic supports inspired by “like grows like” principle

A seeding-free synthesis strategy was developed for the preparation of dense and phase-pure MFI zeolite membranes based on “like grows like” principle. Through covalent modification of the porous ceramic supports by using 1H,1H,2H,2H-perfluoroalkyltriethoxysilanes (POTS), the support surface was changed from hydrophilic to hydrophobic, which promotes the nucleation and growth of hydrophobic MFI zeolite membranes. Thin, well-intergrown and phase-pure MFI zeolite membranes, with a thickness of about 2.0–3.0 μm, can be facilely prepared on POTS-modified supports like Al₂O₃ and TiO₂ at 175 °C for 24 h. No cracks, pinholes or other visible macroscopic defects are observed in the membrane layer. The MFI zeolite membranes were evaluated in the hydrophobic separation of 5.0 wt% ethanol/water mixture at 75 °C by pervaporation. The MFI zeolite membrane prepared on the POTS-modified TiO₂ disk shows high pervaporation separation for ethanol recovery. At 75 °C, a separation factor of 103 and total flux of 2.56 kg/m²h can be obtained, which is promising to extract bio-alcohols from the fermentation broth.