Ethane-selective permeation in mixed matrix membranes containing fluorinated carboxylic acid functionalized metal-organic frameworks

Membrane technology based on ethane-selective permeation materials is highly imperative for energy-efficient separating C2H6 and C2H4 mixture. Herein, we rationally constructed a fluorinated metal-organic framework based mixed matrix membrane (MMM), which can selectively permeate ethane from a C2H6/C2H4 mixture. The unique structure of MOF-808 allows functionalization of fluorinated carboxylic acid (FCA) in the MOF framework to construct various fluorinated MOFs via a facile post-synthetic strategy. As a proof of concept, four FCAs with different fluorocarbon chain lengths, including trifluoroacetic acid (TFA), pentafluoropropionic acid (PFPA), heptafluorobutyric acid (HFBA), and perfluorovaleric acid (PFVA), were used to create fluorinated MOFs and corresponding MMMs. The typical HFBA-MOF/PIM-1 hybrid membrane exhibits a high C2H6/C2H4 selectivity of about 2.3 with C2H6 permeability of 4246 Barrer at 253 K and 6 bar. Computational simulations confirm that the reversed permeation behavior is attributed to the strong affinity of C2H6 within the fluorinated pore environment, mediated by multiple hydrogen bonds.