Solvent-vapor-triggered crystallization of a ZIF-90 membrane with versatile separation properties towards light hydrocarbons

Membrane separation has been well acknowledged as a forward-looking technology for hydrocarbon separation. Zeolitic imidazole framework-90 (ZIF-90) with effective pore size of 5.0 Å is a promising membrane material for hydrocarbon separation. Owing to the enormous challenges facing the fabrication process, the research on the ZIF-90 polycrystalline membrane is fairly underexplored. Herein we report a solvent-vapor-triggered crystallization strategy for the production of ZIF-90 membranes. The resultant ZIF-90 membrane had a typical polycrystalline membrane structure where the regular ZIF-90 grains propagated inside the whole porous support. Intriguingly, the membrane displayed two obvious sharp cut-off regions falling between the C3H6/C3H8 and n-C4H10/i-C4H10 gas pairs, respectively. The ZIF-90 membrane achieved ultrafast and selective permeation of C3H6 from the C3H6/C3H8 mixture. The C3H6 flux was about 3.4 kg·m−2·h−1 which was comparable to the commercial NaA zeolite membrane for organic solvent dehydration. Further, the distinctive gas transport kinetic nature enabled the ZIF-90 membranes to exclude i-C4H10 and thus harvest unprecedented n-/i-C4H10 separation ability in high-temperature regions. As the temperature elevated from 25 to 150 °C, the n-C4H10 permeance was enhanced from 3.0 × 10−9 to 12 × 10−9 mol·m−2·s−1·Pa−1 and the n-C4H10/i-C4H10 separation factors was improved from 63 to 95, respectively. The high permeance and permselectivity at industrially relevant high temperatures and pressures make ZIF-90 membrane attractive for industrial light hydrocarbon separation.