(65g) Unexpectedly High Propylene-Selective Mixed-Matrix Membranes with Additive-Incorporated 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[1]. 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 novel one-step ZIF-8-based asymmetric MMM fabrication strategy, termed “PIMOF”, enabling rapid formation of asymmetric MMMs with relatively high ZIF-8 loadings. 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.

In this presentation, we will introduce a novel approach to enhance the C3 separation performances of asymmetric mixed-matrix membranes (MMMs) made from PIMOF process. The method involves incorporating an additive, sodium formate, which modifies the formation of ZIF-8 filler inside the polymeric matrix. The resulting MMMs with sodium formate exhibit exceptional C₃H₆/C₃H₈ separation factor of 222.5 ± 1.79 and C₃H₆ permeance of 10.1 ± 0.4 GPU, surpassing the majority of high-quality polycrystalline ZIF-8 membranes reported to date. Sodium formate functions as a deprotonator, leading to faster nucleation and small filler particles inside the polymer matrix. These small particles create strong polymer-particle interaction, which limits linker swing motion and further enhances C3 separation performance.

1. Marti, A.M., et al., Simple Fabrication Method for Mixed Matrix Membranes with in Situ MOF Growth for Gas Separation. ACS Applied Materials & Interfaces, 2018. 10(29): p. 24784-24790.