Abstract:

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.

Key words: carboxylated polymer of intrinsic microporosity, mixed matrix membranes, zeolite imidazole framework, high content, CO₂/CH₄ separation

摘要：

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。

关键词: 羧基化自聚微孔聚合物, 混合基质膜, 沸石咪唑酯骨架材料, 高添加量, CO₂/CH₄分离