The Molecular Foundry, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Nano Lett. 2017 Nov 8;17(11):6828-6832. doi: 10.1021/acs.nanolett.7b03106. Epub 2017 Oct 23.
Despite the availability of chemistries to tailor the pore architectures of microporous polymer membranes for chemical separations, trade-offs in permeability and selectivity with functional group manipulations nevertheless persist, which ultimately places an upper bound on membrane performance. Here we introduce a new design strategy to uncouple these attributes of the membrane. Key to our success is the incorporation of phase-change metal-organic frameworks (MOFs) into the polymer matrix, which can be used to increase the solubility of a specific gas in the membrane, and thereby its permeability. We further show that it is necessary to scale the size of the phase-change MOF to nanoscopic dimensions, in order to take advantage of this effect in a gas separation. Our observation of an increase in solubility and permeability of only one of the gases during steady-state permeability measurements suggests fast exchange between free and chemisorbed gas molecules within the MOF pores. While the kinetics of this exchange in phase-change MOFs are not yet fully understood, their role in enhancing the efficacy and efficiency of the separation is clearly a compelling new direction for membrane technology.
尽管有化学物质可用于调整微孔聚合物膜的孔结构以进行化学分离，但在渗透性和选择性与官能团操作之间进行权衡仍然存在，这最终对膜性能施加了上限。在这里，我们引入了一种新的设计策略来解耦膜的这些属性。我们成功的关键是将相变金属-有机骨架（MOF）纳入聚合物基质中，这可以用来增加膜中特定气体的溶解度，从而提高其渗透性。我们进一步表明，有必要将相变 MOF 的尺寸缩小到纳米尺度，以便在气体分离中利用这种效应。我们在稳态渗透性测量中观察到只有一种气体的溶解度和渗透性增加，这表明在 MOF 孔内自由和化学吸附气体分子之间的快速交换。虽然相变 MOF 中的这种交换动力学尚未完全理解，但它们在增强分离效果和效率方面的作用显然是膜技术的一个引人注目的新方向。
