| Summary: | Currently, cellulose acetate (CA) membranes dominate membrane-based CO<sub>2</sub> separation for natural gas purification due to their economical and green nature. However, their lower CO<sub>2</sub> permeability and ease of plasticization are the drawbacks. To overcome these weaknesses, we have developed high-performance mixed matrix membranes (MMMs) consisting of cellulose triacetate (CTA), cellulose diacetate (CDA), and amine functionalized zeolitic imidazolate frameworks (NH<sub>2</sub>-ZIF-8) for CO<sub>2</sub> separation. The NH<sub>2</sub>-ZIF-8 was chosen as a filler because (1) its pore size is between the kinetic diameters of CO<sub>2</sub> and CH<sub>4</sub> and (2) the NH<sub>2</sub> groups attached on the surface of NH<sub>2</sub>-ZIF-8 have good affinity with CO<sub>2</sub> molecules. The incorporation of NH<sub>2</sub>-ZIF-8 in the CTA/CDA blend matrix improved both the gas separation performance and plasticization resistance. The optimized membrane containing 15 wt.% of NH<sub>2</sub>-ZIF-8 had a CO<sub>2</sub> permeability of 11.33 Barrer at 35 °C under the trans-membrane pressure of 5 bar. This is 2-fold higher than the pristine membrane, while showing a superior CO<sub>2</sub>/CH<sub>4</sub> selectivity of 33. In addition, the former had 106% higher CO<sub>2</sub> plasticization resistance of up to about 21 bar and an impressive mixed gas CO<sub>2</sub>/CH<sub>4</sub> selectivity of about 40. Therefore, the newly fabricated MMMs based on the CTA/CDA blend may have great potential for CO<sub>2</sub> separation in the natural gas industry.
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