Hydrophobic MFI membranes with a film thickness of less than 500 nm and a very low amount of defects were grown on α-alumina supports in fluoride media at near neutral pH (denoted TPAF-MFI membrane). These membranes are at least 4 times thinner than previous membranes prepared in fluoride media at near neutral pH; moreover, corresponding separation performance is the first time reported in this paper. For comparison, MFI membranes with a film thickness of about 500 nm were grown in hydroxide media at high pH (denoted TPAOH-MFI membrane). According to the permporometry results, the amount of defects in the TPAF-MFI membranes is about half of that in the TPAOH-MFI membranes, and most of the defects in both membranes are smaller than 1 nm. The membranes were evaluated for separation of a feed of 5 kPa n-butanol and 5kPa water, with 91 kPa helium as balance gas and 101 kPa helium as sweep gas. Both membranes displayed high permeance and the TPAF-MFI membrane was more selective to n-butanol than the TPAOH-MFI membrane. Interestingly, the total permeance and n-butanol/water separation factor increased to 11×10-7 mol/(m2 s Pa) and 19, respectively, after activation of the TPAF-MFI membrane at 300 ˚C in a helium flow saturated with n-butanol at 25 ˚C. The TPAF-MFI membrane also displayed a CO2/H2 separation factor of 6 at 25˚C and a CO2 permeance of 26×10-7 mol/(m2 s Pa) for a feed of 450 kPa CO2 and 450 kPa H2 and 101 kPa helium sweep gas.