Engineering Atomically Precise Nanochannels Using Layered 2D Sheets to Enable Chemical Separation Membranes with Exceptional Permeance and Size-Selectivity

将空气分离成其组分，氧气，氮气，二氧化碳，水蒸气和其他微量气体如氦气，是一个价值数十亿美元的行业。示例包括：在高性能轮胎中使用纯化氮气，并将其注入特种咖啡中;在医疗保健和航天飞机发射中使用纯化氧气;在气球中使用氦气。任何混合物的分离都需要能量和分离一种组分的策略。 尺寸选择性膜提供了一种这样的策略，允许分子以由它们在膜通道内的配合能力、它们的扩散率以及它们与表面相互作用的强度决定的速率渗透通过内部通道。 减少这种表面相互作用会增加渗透，这转化为以较低的能量消耗提高生产率。 无摩擦运输的一个候选者是由碳原子组成的膜通道，例如圆柱形碳纳米管或堆叠的平面石墨烯片。 由于弱的表面相互作用对流动几乎没有阻碍，因此实验表明，水通过碳纳米管的渗透比经典模型预测的大1000倍。然而，紧密堆积的碳纳米管的均匀通道难以大量合成。 支撑的石墨烯片显示出更有希望用于大规模合成，但目前是通过高度氧化的脱层过程从石墨衍生的，这赋予了使无摩擦运输无效的显著残留氧原子。该项目将利用自下而上的非氧化方法来创建支撑石墨烯膜，其具有优化的可控通道，用于小分子的尺寸选择性传输，例如氧气，氮气，氢气，氦气和水。该项目将使用分子间隔物作为支撑剂，在原始未氧化的平行石墨烯片之间合成可控纳米通道。将开发用于精确制造具有范围从2-8埃的亚纳米间隙的纳米通道的稳健化学，以赋予尺寸选择性。候选间隔分子包括帕拉取代的苯衍生物、通过[2+2]环加成接枝的官能团以及非共价吸附的平面和非平面芳烃。将制造隔离的双层通道和多层层压膜。孤立的通道将提供基本的表面科学测量的结构和性能，而多层膜将使宏观测量的运输，以验证无摩擦，无渗透运输的理论预测。微结构表征数据，结合传输测量，将指导设计越来越有效的膜材料。研究生和本科生都将为这个项目进行实验室研究，努力针对代表性不足的群体。这项研究将为针对高中学生的互动课程提供信息，同时向教师传播培训录像。

The separation of air into its components, oxygen, nitrogen, carbon dioxide, water vapor, and other trace gases such as helium, is a billion dollar industry. Examples include: use of purified nitrogen in high performance tires and infusion into specialty coffee; use of purified oxygen for healthcare and the launch space shuttles; use of helium for balloons. Separation of any mixture requires both energy and a strategy to isolate one component. Size selective membranes provide one such strategy, allowing molecules to permeate through internal channels at rates that are dictated by their ability to fit within a membrane channel, their diffusivity, and the strength by which they interact with the surface. Decreasing this surface interaction increases permeation, which translates to an increased production rate at lower energy consumption. One candidate for frictionless transport are membrane channels comprised of carbon atoms, such as cylindrical carbon nanotubes or stacked planar graphene sheets. As weak surface interactions provide little impediment to flow, the permeation of water through carbon nanotubes has been experimentally shown to be 1000 times greater than that predicted from classical models. Yet, homogenous channels of closely packed carbon nanotubes have been difficult to synthesize in large quantities. Propped graphene sheets show more promise for large scale synthesis, but are currently derived from graphite via a highly oxidative delamination process, which imparts significant residual oxygen atoms that invalidate frictionless transport. This project will utilize a bottoms-up nonoxidative approach to create propped graphene membranes with controlled channels optimized for size selective transport of small molecules, such as oxygen, nitrogen, hydrogen, helium, and water.This project will use molecular spacers as proppants to synthesize controlled nanochannels between pristine unoxidized parallel graphene sheets. Robust chemistries will be developed for precisely fabricating nanochannels with sub-nanometer gaps that range from 2-8 Angstroms to impart size selectivity. Candidate spacer molecules include para substituted benzene derivatives, functional groups grafted via [2+2] cycloaddition, and non-covalently adsorbed planar and non-planar aromatic hydrocarbons. Both isolated bilayer channels and multilayered laminate membranes will be fabricated. The isolated channels will afford fundamental surface science measurements of structure and properties whereas the multilayered membranes will enable macroscopic measurements of transport to validate the theoretical prediction of frictionless, ultrahigh permeance transport. Microstructural characterization data, in conjunction with transport measurements, will guide design of increasingly effective membrane materials. Both graduate and undergraduate students will perform laboratory research for this project, with an effort to target underrepresented groups. The research will inform interactive lessons targeted at high school level students, accompanied by dissemination of training videos to teachers.