We exploited ¹²⁹Xe NMR to investigate xenon gas uptake and dynamics in a porous liquid formed by dissolving porous organic cages in a cavity-excluded solvent. Quantitative ¹²⁹Xe NMR shows that when the amount of xenon added to the sample is lower than the amount of cages present (subsaturation), the porous liquid absorbs almost all xenon atoms from the gas phase, with 30% of the cages occupied with a Xe atom. A simple two-site exchange model enables an estimate of the chemical shift of ¹²⁹Xe in the cages, which is in good agreement with the value provided by first-principles modeling. T₂ relaxation times allow the determination of the exchange rate of Xe between the solvent and cage sites as well as the activation energies of the exchange. The ¹²⁹Xe NMR analysis also enables determination of the free energy of confinement, and it shows that Xe binding is predominantly enthalpy-driven.

中文翻译：

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129Xe NMR 阐明多孔液体中的气体吸收和热力学


我们利用 ¹²⁹ Xe NMR 来研究多孔液体中氙气的吸收和动力学，该多孔液体是通过将多孔有机笼溶解在空腔排除溶剂中而形成的。定量 ¹²⁹ Xe NMR表明，当样品中添加的氙量低于存在的笼的量（亚饱和）时，多孔液体从气相中吸收了几乎所有的氙原子，其中30%笼子里有 Xe 原子。简单的双位点交换模型可以估计笼中 ¹²⁹ Xe 的化学位移，这与第一原理模型提供的值非常一致。 T ₂ 弛豫时间可以确定溶剂和笼位点之间 Xe 的交换速率以及交换的活化能。 ¹²⁹ Xe NMR 分析还能够确定约束自由能，并且表明 Xe 结合主要是由焓驱动的。