Study of molecular interfaces in polymer thin-film composite membranes for the efficient gas separations

本研究致力于开发和研究聚合物之间具有选择性分子薄界面的薄膜复合材料（TFC）膜，以实现与其他气体的复杂混合物中二氧化碳（CO2）的有效分离。在第一年，研究正在按照原计划进行。研究的重点是研究水蒸气产生的等离子体对疏水聚合物层的表面改性如何影响与亲水性选择层的选择界面的形成。结果表明，要形成合适的层状结构，必须进行最小临界量的表面改性。此外，发现仅通过等离子体处理的表面修饰不足以提高膜对CO2的选择性。深入研究了CO2、O2和N2的气体输运。发现分子界面的存在是CO2/N2和CO2/O2高选择性分离的重要因素。在TFC结构中加入选择性界面后，CO2/N2和CO2/O2的分离选择性分别提高到35和13左右（在没有选择层和界面的膜中为~10和~5）。最后，本工作的重点是它们在直接空气捕获CO2的膜应用。直接空气捕获是缓解气候变化影响的一项重要技术。通过直接从空气中捕获二氧化碳，我们可以减少大气中温室气体的数量，减缓全球变暖的速度。

This work is devoted to developing and investigating thin-film composite (TFC) membranes with selective molecularly-thin interfaces between polymers to achieve efficient carbon dioxide (CO2) separation from complex mixtures with other gases. During the first year, the research is progressing according to the original plan. The focus was to investigate how the surface modification of the hydrophobic polymer layer by water vapor-generated plasma influences the formation of the selective interface with the hydrophilic selective layer. It was found that some minimum critical amount of surface modification is essential to form the proper laminate structure. Furthermore, the influence of surface modification by the plasma treatment alone was found insufficient to increase the membrane's selectivity towards CO2.The gas transport of CO2, O2, and N2 was thoroughly studied. The existence of the molecular interface was found to be the essential factor in the highly selective CO2/N2 and CO2/O2 separation. With the inclusion of the selective interface in the structure of the TFC, the selectivity increased to about 35 and 13 for CO2/N2 and CO2/O2 separation, respectively (~10 and ~5 in the membranes without the selective layer and interface). Finally, this work focuses on their membrane application for the direct air capture of CO2. Direct air capture is an important technology to mitigate the effects of climate change. By capturing carbon dioxide directly from the air, we can reduce the amount of greenhouse gases in the atmosphere and slow down the rate of global warming.