(373n) Improving Propylene/Propane Separation Performances of Polycrystalline ZIF-8 Membranes Via Additive-Assisted Microstructural Modification

Due to their promising propylene/propane (C3) separation, polycrystalline ZIF-8 membranes have been extensively studied for the last decade.[1] Because of the nature of the polycrystalline membranes, however, it is of critical importance to control the grain boundary structures (defects) of ZIF-8 membranes to ensure high reproducibility and separation performance.[2] There are two ways to obtain improved grain boundary structures: 1) improving synthesis methods and 2) healing defects by post-synthetic processing.

In this presentation, we plan to show how a simple addition of an additive can modify crystal growth and improve the microstructures of polycrystalline ZIF-8 membranes, thereby improving their C3 separation performances. ZIF-8 membranes were prepared using our previously-reported microwave-assisted seeding and secondary growth method.[3] We found that when a diol-based additive was added into the secondary growth solution, the grains of the ZIF-8 membranes exhibited unusual plate-like morphology. The resulting ZIF-8 membranes showed significantly improved C3 separation performances as compared with the neat membranes synthesized without the additive, showing impressively high C3 separation factor of ~ 283 with the propylene permeability of ~ 12.4 Barrer. The ZIF-8 membranes outperform most of previously reported high-quality polycrystalline ZIF-8 membranes. The high separation performance of the membranes was attributed to enhanced grain boundary structures resulting from plate-like ZIF-8 grains.

References

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

[2] 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.

[3] 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.