In this work, we investigated the pervaporation separation performance of an ethanol – cyclohexane mixture using a thin-film composite membrane based on a heat-treated, o-hydroxyl-substituted polyimide of intrinsic microporosity (PIM-6FDA-OH). We report in detail the complex chemical and structural transformations that are associated with the development of thermally-rearranged (TR, 400–450 °C), and carbon molecular sieve (CMS) membranes (>500 °C). These transformations strongly affect the affinity-related (e.g. swelling behavior) and morphology-related (e.g. microporosity) properties of the TR and CMS membrane materials which translate into a complex molecular-level separation behavior toward an organic solvent mixture during pervaporation. We show that excellent separation performance (total flux ∼ 4 kg/m²h and ethanol/cyclohexane separation factor of ∼1250) can be achieved after precise thermal treatment at the onset of the CMS formation. In addition, we highlight the unique property of pervaporation where, in contrast to liquid solvent permeation, the downstream side of the membrane remains essentially dry due to exposure to high vacuum. As a result, a sharp molecular cut-off can be achieved within this dry downstream region of the membrane despite considerable overall swelling/penetrant concentration in the upstream region of the membrane.

在这项工作中，我们使用基于热处理的邻聚酰亚胺（ PIM-6FDA-OH）的薄膜复合膜研究了乙醇-环己烷混合物的渗透汽化分离性能。我们详细报告了与热重排（TR，400–450 °C）和碳分子筛（CMS）膜（> 500 °C）的发展相关的复杂化学和结构转变。这些转变强烈影响 TR 和 CMS 膜材料的亲和相关（例如溶胀行为）和形态相关（例如微孔性）特性，这些特性转化为对有机溶剂的复杂分子级分离行为渗透蒸发过程中的混合物。我们表明，在 CMS 形成开始时进行精确热处理后，可以实现出色的分离性能（总通量约 4 kg/m ²此外，我们强调了渗透蒸发的独特性质，与液体溶剂渗透相比，膜的下游侧由于暴露在高真空中而保持基本干燥。结果，尽管在膜的上游区域中总体溶胀/渗透剂浓度相当大，但在膜的干燥下游区域内可以实现急剧的分子截断。