(642d) Microstructural Modification of Polycrystalline ZIF-8 Membranes By an Additive for Enhanced Propylene/Propane Separation Performance

Since the first ZIF-8 polycrystalline membranes showed promising propylene/propane (C3) separation in 2012,[1] there have been extensive works for the last decade to produce high quality ZIF-8 membranes.[2] Due to the nature of the polycrystalline materials, however, it is of critical importance to improve the grain boundary structures (defects) of ZIF-8 membranes to achieve high separation performance and reproducibility.[3] There are two approaches to control grain boundary structures: 1) modifying ZIF-8 synthesis methods and 2) post-synthetic processing to heal the defects.

In this talk, we plan to present how a simple addition of an additive can effectively improve the microstructures of polycrystalline ZIF-8 membranes, thereby enhancing their C3 separation performances. ZIF-8 membranes were fabricated from our previously-reported microwave-assisted seeding and secondary growth method.[4] We found that when a diol-based additive was added into the secondary growth solution, the grains of the ZIF-8 membranes showed unusual plate-like morphology. The resulting ZIF-8 membranes exhibited significantly improved C3 separation performances as compared with the neat ZIF-8 membranes synthesized without the additive, showing impressively high C3 separation factor of ~ 283 with the propylene permeability of ~ 12.4 Barrer. The separation factor of ZIF-8 membranes in this work outperformed most of previously reported high-quality polycrystalline ZIF-8 membranes. The high performance of the membranes was attributed to improved grain boundary structures resulting from plate-like ZIF-8 grains.

References

[1] Y. Pan, T. Li, G. Lestari, Z. Lai, Effective separation of propylene/propane binary mixtures by ZIF-8 membranes, Journal of Membrane Science 390 (2012) 93-98.

[2] H.K. Jeong, Metal–organic framework membranes: Unprecedented opportunities for gas separations, AIChE Journal 67(6) (2021) e17258.

[3] Y. Ren, X. Liang, H. Dou, C. Ye, Z. Guo, J. Wang, Y. Pan, H. Wu, M.D. Guiver, Z. Jiang, Membrane‐Based Olefin/Paraffin Separations, Advanced Science 7(19) (2020) 2001398.

[4] H.T. Kwon, H.-K. Jeong, Highly propylene-selective supported zeolite-imidazolate framework (ZIF-8) membranes synthesized by rapid microwave-assisted seeding and secondary growth, Chemical Communications 49(37) (2013) 3854-3856.