Zeolite molecular sieves are widely used in gas separation and shape-selective catalysis, but these applications often require discriminating differences as little as 0.1 Å. Molecular sieving with such size selectivity demands zeolites with highly tunable pore diameters and adsorption properties, which are technically challenging to prepare. Nevertheless, it is shown that a wide range of organic functional groups can be covalently functionalized onto the interior pore walls of the zeolites, MOR, LTL, FAU, and MFI, to systematically “tune” their effective pore diameters with respect to the size of organic groups. For organic functionalization, small and aggressive organic electrophiles are used (e.g., organo-halide and -diazonium) as grafting agents, which are accessible to the intracrystalline void space, forming a C–O_zeolite bond in a reaction with a bridging oxygen as proved by multiple analysis data. It is demonstrated that the post-functionalization can be used to tailor the molecular sieving action of a parent zeolite to give size-selective adsorbents for light olefin/paraffin separations. 4-Methoxybenzene-functionalized MOR separates ethylene from ethane with an ideal-adsorbed-solution-theory selectivity of ≈5873, whereas toluene-grafted MOR completely separates propylene/propane mixtures. Therefore, tailoring the molecular-sieving properties of zeolites by organic functionalization broadens their applications to challenging separations.

中文翻译：

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合成后功能化能够微调沸石的分子筛特性，用于轻质烯烃/石蜡分离

沸石分子筛广泛用于气体分离和形状选择性催化，但这些应用通常需要低至 0.1 Å 的区分差异。具有这种尺寸选择性的分子筛需要具有高度可调孔径和吸附性能的沸石，这在技术上具有挑战性。然而，研究表明，广泛的有机官能团可以共价官能化到沸石、MOR、LTL、FAU 和 MFI 的内孔壁上，以系统地“调整”它们的有效孔径与有机基团。对于有机功能化，使用小而强的有机亲电试剂（例如，有机卤化物和重氮）作为接枝剂，它们可进入晶内空隙空间，形成 C-O多项分析数据证明，_沸石键与桥接氧反应。结果表明，后官能化可用于调整母体沸石的分子筛分作用，从而为轻质烯烃/石蜡分离提供尺寸选择性吸附剂。4-甲氧基苯官能化的 MOR 以 ≈5873 的理想吸附溶液理论选择性将乙烯与乙烷分离，而甲苯接枝的 MOR 可完全分离丙烯/丙烷混合物。因此，通过有机功能化来调整沸石的分子筛分特性将其应用范围扩大到具有挑战性的分离。