(373q) Unexpectedly High Propylene-Selective Mixed-Matrix Membranes with Facile in-Situ ZIF-8 Filler Formation Process

In-situ MMM fabrication is an emerging strategy that might potentially overcome the limitations of the conventional blending methods. In this regard, metal-ogranic frameworks (MOFs) offer unique opportunity for in-situ MMM fabrication due to their labile chemistry and organic moieties that are compatible with polymers. Zeolitic-imidazolate framework-8 (ZIF-8), consisting of a zinc center tetrahedrally coordinated with 2-methylimidazolate linkers, is one of the most promising molecular sieve materials for propylene/propane separation. Recently, our group developed a scalable mixed-matrix membranes fabrication strategy using in-situ Zif-8 formation approach, named PMMOF[1], which enables formation of MMMs not only with improved gas separation performances but also in a scalable geometry (i.e., asymmetric hollow fibers with submicron thick selective MMM skin layers)[2]. However, the PMMOF suffers from two major challenges such as relatively complicated fabrication steps and limited choice of polymer matrices (i.e., polyimide-based polymers).

In this presentation, a novel second-generation PMMOF is promoted to address the challenges of the first-generation. The new process, termed “PIMOF”, enable rapid formation of high ZIF-8 loaded (> 50 wt%) 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, comparable even with polycrystalline ZIF-8 membranes. The unexpectedly high C3 performance of the membranes was attributed to the uniform distribution of the extremely small ZIF-8 nanoparticles (~ 5-10 nm) in the selective skin layers and improved molecular sieving properties of the ZIF-8 nanofillers resulting from the hindered linker flexibility upon confined filler formation.

Reference:

1. 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.
2. 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.