The separation of xylene isomers is of vital importance in chemical industry but remains challenging due to their similar structure and overlapping physiochemical properties. Membrane-based separations using the zeolite MFI, graphene oxide, and metal–organic frameworks have been intensively studied for this application, but the performance is limited by the well-known rule that the filtrate permeance scales inversely with the membrane thickness. We propose a novel membrane design that is capable of breaking this rule, based on an array of recently discovered zeolite nanotubes. Each zeolite nanotube possesses a 3.6-nm-wide central channel, connecting to dense, uniform 0.8-nm-wide holes on its wall that act as selective pores. Comprehensive molecular dynamics simulations show that this membrane exhibits permeance exceeding current state-of-the-art membranes by at least an order of magnitude while simultaneously maintaining an acceptable selectivity. In particular, a thicker membrane featuring longer zeolite nanotubes exhibits a higher permeance due to the presence of more selective pores. The proposed membrane design is expected to be broadly applied to other gas separations and even desalination as long as zeolitic nanotubes with customized pores are available.

中文翻译：

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使用沸石纳米管阵列膜极快地分离二甲苯异构体

二甲苯异构体的分离在化学工业中至关重要，但由于其相似的结构和重叠的理化性质，仍然具有挑战性。使用沸石 MFI、氧化石墨烯和金属有机骨架的膜分离已针对该应用进行了深入研究，但其性能受到众所周知的规则的限制，即滤液渗透率与膜厚度成反比。我们提出了一种新颖的膜设计，它基于最近发现的一系列沸石纳米管，能够打破这一规则。每个沸石纳米管都有一个 3.6 纳米宽的中心通道，连接到其壁上密集、均匀的 0.8 纳米宽的孔，这些孔充当选择性孔。全面的分子动力学模拟表明，该膜的渗透性比当前最先进的膜至少高一个数量级，同时保持可接受的选择性。特别是，由于存在更多选择性孔，具有较长沸石纳米管的较厚膜表现出更高的渗透性。只要具有定制孔的沸石纳米管可用，所提出的膜设计预计将广泛应用于其他气体分离甚至海水淡化。