Effect of Activation Process on the Performance of ZIF‐8 Membrane for Propylene/Propane Separation

Abstract

Fine‐tuning the interior structure of porous materials is desirable for altering the gas transport characteristic. An activation‐induced structure manipulation strategy is reported here to act on ZIF‐8 membranes for C3H6/C3H8 separation. Notably, after treatment with methanol, acetonitrile and chloroform, the amount of embedded N,N‐dimethylacetamide (DMAc) molecules within ZIF‐8 cavity is about 0.8, 1.2 and 3.8 molecules per cage, respectively. The increased amount of DMAc results in enhanced thermodynamic adsorption selectivity of ZIF‐8 for C3H6/C3H8, which is highly constructive to the separation ability of corresponding ZIF‐8 membranes. Typically, the ZIF‐8 membranes activated with methanol, acetonitrile and chloroform demonstrate C3H6 permeance of 1.5 · 10−8, 8.5 · 10−9 and 4.3 · 10−9 mol m−2s−1Pa−1, and C3H6/C3H8 separation factors of 52, 92 and 192, respectively.

Fabrication of Polycrystalline Zeolitic Imidazolate Framework Membranes by a Vapor-Phase Seeding Method

“…Although in situ synthesis is straightforward, it often produces relatively thick membranes with moderate gas permeances. In comparison, seeded growth can produce thinner membranes, but it often requires the creation of a homogeneous seed layer [ 18 , 19 , 20 , 21 ]. Therefore, various seeding techniques have been developed, including spin-coating [ 22 ], manual rubbing [ 23 ], dip-coating [ 24 , 25 , 26 , 27 ], thermal seeding [ 28 ], microwave seeding [ 29 , 30 , 31 , 32 , 33 ], vacuum filtration [ 34 ], and the use of sacrificial of ZIF-L as the seed layer [ 35 ].…”