Soft porous crystals (SPCs) are novel porous materials that exhibit significant global crystal structure deformations under external stimuli. The crystal structure deformation brings strong switch effects and hysteresis effects, which can be used to achieve highly selective separations for similar gas molecules. Among SPCs, soft porous organic cages (POCs) are particularly interesting due to their unique advantages in stability and processability. The soft nonbonding interactions in POCs lead to more delicate structural deformations and complicated sorption isotherms. Therefore, compared to rigid porous materials, it is more difficult to understand, predict, and rationally control the gas uptakes of POCs. In this work, we advance this field by employing a hybrid Grand Canonical Monte Carlo/Molecular Dynamics strategy to investigate the unique sorption behavior of a POC, named NKPOC-1, upon exposure to CO₂. The experimental multistep sorption isotherms with large hysteresis at different temperatures are well reproduced. We further elucidate the distinct sorption and crystal structure deformation mechanisms at different temperatures, demonstrating the unusual complexity of POC gas adsorption. To the best of our knowledge, this is the first thorough theoretical study of understanding the sorption mechanism of soft POCs. Also, the methodology used in this work provides a generally effective way to simulate the adsorption behaviors in highly flexible materials.

中文翻译：

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NKPOC-1 中二氧化碳吸收的分子动力学模拟：了解软多孔分子晶体中温度依赖性多步吸附


软多孔晶体（SPC）是一种新型多孔材料，在外部刺激下表现出显着的整体晶体结构变形。晶体结构变形带来强烈的开关效应和滞后效应，可用于实现相似气体分子的高选择性分离。在SPC中，软质多孔有机笼（POC）因其在稳定性和加工性能方面的独特优势而特别令人感兴趣。 POC 中的软非键相互作用导致更微妙的结构变形和复杂的吸附等温线。因此，与刚性多孔材料相比，理解、预测和合理控制POCs的气体吸收量更加困难。在这项工作中，我们通过采用混合大正则蒙特卡罗/分子动力学策略来研究 POC（名为 NKPOC-1）在暴露于 CO ₂ 时的独特吸附行为，从而推进了这一领域的发展。在不同温度下具有大滞后的实验多步吸附等温线得到了很好的再现。我们进一步阐明了不同温度下不同的吸附和晶体结构变形机制，证明了 POC 气体吸附的异常复杂性。据我们所知，这是首次深入了解软 POC 吸附机制的理论研究。此外，这项工作中使用的方法提供了一种模拟高柔性材料中吸附行为的普遍有效的方法。