(354a) ZIF-8-Containing Asymmetric Mixed-Matrix Membranes with Unexpectedly High Propylene/Propane Separation Performance By an Innovative One-Step Process

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]. However, the PMMOF suffers from two major challenges: 1) multi-step involved that are relatively complicated and 2) limited choice of polymer matrices (i.e., polyimide-based polymers).

In this presentation, we plan to present a novel second-generation one-step MOF-based asymmetric MMM fabrication strategy, addressing the challenges of the first-generation PMMOF process. The new process, termed “PIMOF”, enable rapid formation of ZIF-8-containing asymmetric MMMs. The as-prepared MMMs showed unprecedentedly high C₃H₆/C₃H₈ (C3) separation performance as compared to other propylene-selective MMMs reported so far with the C₃H₆ permeance of ~ 7.5 GPU and C₃H₆/C₃H₈ separation factor of ~ 107. It is worthy of noting that our MMMs exhibit comparable C3 separation performances with polycrystalline ZIF-8 membranes. The unexpectedly high C3 performance of the membranes was attributed to 1) unusually high ZIF-8 nanofiller loading in the selective skin layers and 2) improved molecular sieving properties of the ZIF-8 nanofillers resulting from the hindered linker flexibility upon confined filler formation.

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.