Effective and economical carbon dioxide-methane separation (CO₂/CH₄) is highly desirable in several industries such as sweetening natural gases and renewable natural gas (RNG) from biogas and landfills. Among the different separation technologies, membrane separation has been shown to have lower cost of production and lower CH₄ losses. In this study, Zeolitic Imidazole Frameworks (ZIF-8) crystals with sizes varying from 45 nm to 450 nm were synthesized and incorporated in the polymer of intrinsic microporosity, PIM-1, to form mixed matrix membranes (MMMs). The structure, morphology, and physicochemical properties of the MMMs were characterized by ¹H NMR, FTIR, XRD, TGA, and SEM. ZIF-8 crystal size was controlled using the concentration of sodium formate. The influence of the ZIF-8 crystal size on MMMs was studied by sorption, gas permeability, and aging of the membranes. The MMMs with ZIF-8 crystals of 120 nm particle diameter yielded the greatest improvement in gas transport properties; the CO₂/CH₄ selectivity-CO₂ permeability was 11.4 and 9700 Barrer compared to PIM-1 with 6.4 and 9300 Barrer respectively. The former is near the Robeson 2008 upper bound, while PIM-1 is on the 1991 upper bound. After 40 days of aging, selectivity increased and permeability decreased; the changes were parallel to the Robeson upper bounds indicating increased polymer packing and diffusivity selectivity.

在一些行业中，例如从沼气和垃圾填埋场脱硫天然气和可再生天然气（RNG）的行业中，非常需要有效而经济的二氧化碳-甲烷分离（CO ₂ / CH ₄）。在不同的分离技术中，膜分离已被证明具有较低的生产成本和较低的CH ₄损失。在这项研究中，合成了尺寸在45 nm至450 nm之间的沸石咪唑骨架（ZIF-8）晶体，并将其掺入具有固有微孔性的聚合物PIM-1中，以形成混合基质膜（MMM）。MMM的结构，形态和理化特性由¹表征1 H NMR，FTIR，XRD，TGA和SEM。使用甲酸钠的浓度控制ZIF-8晶体的大小。ZIF-8晶体尺寸对MMM的影响通过膜的吸附，透气性和老化来研究。具有120 nm粒径的ZIF-8晶体的MMM的气体传输性能得到了最大的改善。CO ₂ / CH ₄选择性-CO ₂渗透率分别为11.4和9700 Barrer，而PIM-1分别为6.4和9300 Barrer。前者在Robeson 2008上限附近，而PIM-1在1991上限附近。老化40天后，选择性增加，渗透率降低；这些变化与Robeson上限平行，表明聚合物堆积和扩散率选择性增加。