用于CO2/CH4分离的cPIM-1/ZIF-8混合基质膜的制备

ZIF-8 filled carboxylated polymer of intrinsic microporosity membranes for CO/CH separation

自聚微孔聚合物(PIM-1)虽具有良好的CO2渗透性能,但其气体选择性普遍较差,限制其在CO2/CH4分离领域的应用。本文以N,N-二甲基甲酰胺(DMF)为溶剂制备ZIF-8纳米粒子,将其引入到羧基化的PIM-1基质中,制备了cPIM-1/ZIF-8混合基质膜,用于CO2/CH4分离。结果表明:由于合成ZIF-8的溶剂也是cPIM-1的良溶剂,使得两者之间具有良好的界面相容性,从而使ZIF-8添加量高达质量分数45%。随着ZIF-8添加量的增加,膜的CO2渗透速率持续增加,CO2/CH4选择性呈现先上升后下降的趋势。当ZIF-8添加量为质量分数25%时,膜的CO2/CH4分离性能最好,即CO2渗透系数为3942 Barrer,CO2/CH4选择性为18.7,较cPIM-1纯膜分别提高了84%和43%,成功地超越了Robeson分离上限。

Polymers of intrinsic microporousity(PIMs), especially PIM-1, is very promising membrane materials for CO2 separation due to its high CO2 permeability. However, low gas selectivity such as CO2/CH4 limits its further application in CO2/CH4 separation. In order to solve this problem, zeolitic imidazolate framework-8(ZIF-8) synthesized in DMF was incorporated into carboxylated PIM-1(cPIM-1) matrix to prepare cPIM-1/ZIF-8 mixed matrix membranes(MMMs). Compared with traditional PIM-1-based MMMs, cPIM-1 had good interfacial compatibility with ZIF-8 since it can be well dissolved in DMF, resulting in very high ZIF-8 content(45%) in cPIM-1/ZIF-8 MMMs. With increase of ZIF-8 content, the CO2 permeability of the prepared MMMs monotonically increases, while the CO2/CH4 selectivity was ascend in first and descend at last. At the 25% of ZIF-8 content, the prepared MMMs exhibited the optimal CO2/CH4 separation performance that the CO2 permeability and CO2/CH4 selectivity were 3942 Barrer and 18.7, respectively. Compared with pure cPIM-1 membrane, the CO2 permeability and CO2/CH4 selectivity of cPIM-1/ZIF-8-25 were increased by 84% and 43%, respectively, which exceeded the Robeson upper limit.