Hierarchically microporous membranes for highly energy-efficient gas separations

The implementation of synthetic polymer membranes in gas separations,ranging from natural gas sweetening,hydrogen separation,helium recovery,carbon capture,oxygen/nitrogen enrichment,etc.,has stimulated the vigorous development of high-performance membrane materials.However,size-sieving types of synthetic polymer membranes are frequently subject to a trade-off between permeability and selectivity,primarily due to the lack of ability to boost fractional free volume while simultaneously controlling the micropore size distribution.Herein,we review recent research progress on microporosity manipulation in high-free-volume polymeric gas separation membranes and their gas separation performance,with an emphasis on membranes with hourglass-shaped or bimodally distributed microcavities.State-of-the-art strategies to construct tailorable and hierarchically microporous structures,microporosity characterization,and microcavity architecture that govern gas separation performance are systematically summarized.

MOF基混合基质气体分离膜界面作用调控研究进展

混合基质膜结合了无机填充材料和聚合物组分的双重优势,被认为是一种可同时增加渗透性和选择性的新型方法,有望解决传统聚合物膜的Trade-off效应。混合基质膜的气体分离性能主要依赖无机填充材料的分子筛分性质和高分子本身的化学结构,因此适当选择无机填充材料对于制备高性能的混合基质膜十分重要。金属有机骨架(MOF)作为一种新型多孔填料,具有比表面积大、密度小、孔隙率高和孔尺寸可调等优点,因此在气体吸附分离和气体储存等领域应用广泛,为新型混合基质膜带来良好的发展机遇。但混合基质膜的分离性能并不是简单地两相性能相加,在大多数情况下分离性能远低于材料模拟的预测理论值,造成这种非理想性的关键因素之一是MOF晶体和聚合物之间的界面缺陷,这可能导致界面非选择性空隙的形成、聚合物硬化和孔隙堵塞等界面问题,降低膜的分离性能。因此,实现MOF-聚合物基质间的界面作用调控以改善界面相容性是充分发挥MOF基混合基质膜气体分离潜力的关键。本工作综述了MOF基混合基质膜近五年关于不同类型界面作用调控的方法及策略,及其对气体分离性能的影响。最后,总结构建的界面作用对于混合基质膜性能的正面影响并提出当中存在的问题,为混合基质膜未来的发展提供指导,并激励研究人员采取更多的策略来解决目前的挑战。