Abstract:

The effects of adsorption and separation of O₂/He mixture by two metal-organic frame (MOFs) materials, HKUST-1 and UiO66, were studied by using the Monte Carlo method in molecular simulation. The adsorption isotherms of He and O₂ pure gas were calculated at different temperatures of 150K, 200K and 298K, and the corresponding adsorption heat and adsorption potential energy distribution were also calculated, and then the Idea Adsorbed Solution Theory (IAST) was used to calculate the adsorption selectivity of O₂/He mixture with different helium content in the two MOFs materials. The results showed that both materials exhibited a clear preferential adsorption characteristic of O₂. For three types of O₂/He mixed gases with He volume fraction of 20%, 50% and 80% , the selective adsorption coefficient of HKUST-1 for O₂ relative to He was generally higher than UiO66 at all three temperatures. Both materials indicated more significant selective adsorption at lower temperatures and their selective adsorption coefficients for O₂ relative to He decreased with increasing pressure. At the same time, this coefficient also increased with increasing helium content in the mixed gas. In response to these phenomena, the calculated adsorption heat and adsorption potential energy distribution curves were analyzed.

Key words: separation, molecular simulation, adsorption, metal-organic frame, helium, oxygen

摘要：

应用分子模拟中的蒙特卡洛方法研究了HKUST-1和UiO66两种金属-有机框架（MOFs）材料对O₂/He混合气体的吸附分离效果。对两种材料在150K、200K和298K三种不同温度下吸附He和O₂纯气体的吸附等温线进行了模拟计算，同时计算了相应的吸附热和吸附势能分布，然后使用理想溶液吸附理论（IAST），对三种温度下不同含氦量的O₂/He混合气体在两种MOFs材料中的吸附选择性进行了计算。结果表明：两种材料均对O₂表现出明显优先吸附的特点，对于He体积分数20%、50%和80%的三种O₂/He混合气体，三种温度下HKUST-1对O₂相对于He的选择性吸附系数总体上高于UiO66。两种材料在较低温度下表现出的选择吸附性更加明显，且对O₂相对于He的选择性吸附系数均随压力的提高而降低，同时该系数还随混合气体含氦量增加而提高。针对这些现象，对计算出的吸附热和吸附势能分布曲线进行了分析。

关键词: 分离, 分子模拟, 吸附, 金属-有机框架, 氦气, 氧气