Ho Tuan A, Wang Yifeng, Rempe Susan B, Dasgupta Nabankur, Johnston Cliff T, Xu Guangping, Zwier Timothy S, Mills Melissa
Geochemistry Department, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
Nuclear Waste Disposal Research and Analysis Department, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
J Phys Chem Lett. 2023 Mar 23;14(11):2901-2909. doi: 10.1021/acs.jpclett.3c00291. Epub 2023 Mar 16.
Numerous experimental investigations indicated that expansive clays such as montmorillonite can intercalate CO preferentially into their interlayers and therefore potentially act as a material for CO separation, capture, and storage. However, an understanding of the energy-structure relationship during the intercalation of CO into clay interlayers remains elusive. Here, we use metadynamics molecular dynamics simulations to elucidate the energy landscape associated with CO intercalation. Our free energy calculations indicate that CO favorably partitions into nanoconfined water in clay interlayers from a gas phase, leading to an increase in the CO/HO ratio in clay interlayers as compared to that in bulk water. CO molecules prefer to be located at the centers of charge-neutral hydrophobic siloxane rings, whereas interlayer spaces close to structural charges tend to avoid CO intercalation. The structural charge distribution significantly affects the amount of CO intercalated in the interlayers. These results provide a mechanistic understanding of CO intercalation in clays for CO separation, capture, and storage.
大量实验研究表明，诸如蒙脱石之类的膨胀性黏土能够优先将CO插入其层间，因此有可能作为一种用于CO分离、捕获和储存的材料。然而，对于CO插入黏土夹层过程中的能量-结构关系仍缺乏了解。在此，我们使用元动力学分子动力学模拟来阐明与CO插入相关的能量态势。我们的自由能计算表明，CO从气相中有利地分配到黏土夹层中的纳米受限水中，导致黏土夹层中CO/H₂O的比例相对于 bulk water中的比例增加。CO分子倾向于位于电荷中性的疏水硅氧烷环的中心，而靠近结构电荷的层间空间往往会避免CO插入。结构电荷分布显著影响层间插入的CO量。这些结果为黏土中CO插入用于CO分离、捕获和储存提供了机理上的理解。
