(578f) Scalable Fabrication of MOF-Based Mixed-Matrix Membranes with High Propylene/Propane Separation Performance Using a Polymer Modification Strategy

Due to their potential, mixed-matrix membranes (MMMs) have been extensively studied for the last three decades or so[1]. There are, however, no commercially available MMMs due to their engineering challenges for scalable MMM fabrication[2, 3]. Recently, our group developed a scalable mixed-matrix membranes fabrication strategy using in-situ filler formation approach, named PMMOF[4]. The PMMOF decouples the membrane formation step from the filler incorporation step using an in-situ filler formation in the polymer, enabling formation of MMMs not only with much improved gas separation performances[4] but also in a scalable geometry (i.e., asymmetric hollow fibers with submicron thick selective MMM skin layers)[5].

In this presentation, we plan to present this novel scalable MOF-based MMM fabrication strategy, addressing the challenges of the conventional MMM formation process. The PMMOF process contains four steps: hydrolysis, ion exchange, ligand treatment and imidization. The first step of the process is hydrolysis of a PI by cleaving heterocyclic imide rings in a base solution which turns a PI into a PAA sodium salt (PAA-Na). Followed by exchanging of Na ions with Zn ions, forming PAA zinc salt (PAA-Zn). Solvothermal treatment of the PAA-Zn in an organic ligand, Hmim, solution leads to in situ formation of ZIF-8 in the PAA-Zn (PAA-Zn/ZIF-8). Finally, the PAA-Zn-containing ZIF-8 is thermally imidized, resulting in a PI/ZIF-8 composite film. By varying the zinc concentration in an exchange solution, the ZIF-8 concentration increased up to 32.9 vol %. The resulting 6FDA-DAM/ZIF-8 MMMs showed a much higher C₃H₆/C₃H₈ separation factor (permeability: ~3.4 barrer; separation factor: ~38) than the conventionally prepared 6FDA-DAM/ZIF-8 MMMs and meets the industrial interest.

Reference:

1. Galizia, M., et al., 50th Anniversary Perspective: Polymers and Mixed Matrix Membranes for Gas and Vapor Separation: A Review and Prospective Opportunities. Macromolecules, 2017. 50(20): p. 7809-7843.
2. Dong, G., H. Li, and V. Chen, Challenges and opportunities for mixed-matrix membranes for gas separation. Journal of Materials Chemistry A, 2013. 1(15): p. 4610-4630.
3. Koros, W.J., Gas separation membranes: needs for combined materials science and processing approaches. Macromolecular Symposia, 2002. 188(1): p. 13-22.
4. Park, S., M.R. Abdul Hamid, and H.-K. Jeong, Highly Propylene-Selective Mixed-Matrix Membranes by in Situ Metal–Organic Framework Formation Using a Polymer-Modification Strategy. ACS Applied Materials & Interfaces, 2019. 11(29): p. 25949-25957.
5. Park, S. and H.-K. Jeong, Transforming polymer hollow fiber membrane modules to mixed-matrix hollow fiber membrane modules for propylene/propane separation. Journal of Membrane Science, 2020. 612: p. 118429.