In-situ growth of ZIF-8 nanoparticles in Pebax-2533 for facile preparation of high CO2-selective mixed matrix membranes

In this work, ZIF-8 nanoparticles were introduced into the Pebax-2533 via a novel "in-situ growth" synthesis approach for easy and fast fabrication of the mixed-matrix-membranes (MMMs) with superior CO2 separation performance. The ZIF-8 nanoparticles were grown and formed in the Pebax solution medium by reacting Zn and imidazole via a one-step procedure (without using any sonication in the preparation procedure). The in-situ prepared ZIF-8 particles in Pebax-2533 have suitable dispersion in the matrix and appropriate polymer-filler interfacial compatibility. As ZIF-8 in-situ synthesized, due to the formation of strong filler/polymer interfacial interactions, the crystallinity and Tg of the membrane severely increased, and FFV simultaneously decreased. The in-situ MMMs revealed promising gas separation performance via a synergistic enhancement in the CO2 permeability and selectivity and proved that they have premiere CO2 selectivity than the ex-situ MMMs. For example, the CO2 permeability, and CO2/N2 and CO2/CH4 selectivities enhanced from 57.5 Barrer, 23.4, and 10.6 for the neat Pebax membrane to 73.3 Barrer (28% enhancement), 82 (250%), 32.6 (208%) for the in-situ Pebax/ZIF-8 MMM containing 8 wt% of nano-filler. In the mixed gas experiments, the gas permeabilities were a little lower than the single gas permeabilities, while the selectivities enhanced due to the competitive sorption between the gas molecules, especially for the in-situ MMMs. The in-situ MMM containing 16 wt% of ZIF-8 also surpassed the upper bound-2019. Furthermore, this study indicated the undeniable potential of the in-situ synthesis approach for the fabrication of high CO2 separation performance membranes with a performance stability in the 24 h permeation test for industrial applications, which is available with a snappier and more convenient manufacturing method than the conventional MMMs.