通过埃孔的指数选择性分子筛
Exponentially selective molecular sieving through angstrom pores
摘要：
具有埃级孔的二维晶体被广泛认为是下一代分子分离技术的候选者，该技术旨在提供与高流速相结合的极端的、指数级大的选择性。没有这样的孔已被实验证明。在这里，我们研究通过低强度暴露于低kV电子所产生的单个石墨烯孔的气体传输。氦和氢很容易通过这些孔隙渗透，而较大的物种，如氙和甲烷，实际上被阻挡。渗透气体经历随着分子的动力学直径二次方地增加的活化势垒，并且所产生的孔的有效直径估计为约2埃，约一个缺失的碳环。我们的工作揭示了严格的条件，实现长期追求的指数选择性使用多孔二维膜，并建议限制其可能的性能。
英文摘要：
Two-dimensional crystals with angstrom-scale pores are widely considered as candidates for a next generation of molecular separation technologies aiming to provide extreme, exponentially large selectivity combined with high flow rates. No such pores have been demonstrated experimentally. Here we study gas transport through individual graphene pores created by low intensity exposure to low kV electrons. Helium and hydrogen permeate easily through these pores whereas larger species such as xenon and methane are practically blocked. Permeating gases experience activation barriers that increase quadratically with molecules' kinetic diameter, and the effective diameter of the created pores is estimated as ~2 angstroms, about one missing carbon ring. Our work reveals stringent conditions for achieving the long sought-after exponential selectivity using porous two-dimensional membranes and suggests limits on their possible performance.
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