物理化学学报 >> 2010, Vol. 26 >> Issue (01): 175-182.doi: 10.3866/PKU.WHXB20100111

量子化学及计算化学 上一篇    下一篇

镁锡水滑石中的超分子作用

姚萍, 倪哲明, 胥倩, 毛江洪, 刘晓明, 王巧巧   

  1. 浙江工业大学化学工程与材料学院, 先进催化材料实验室, 杭州 310032
  • 收稿日期:2009-06-01 修回日期:2009-11-01 发布日期:2009-12-29
  • 通讯作者: 倪哲明 E-mail:jchx@zjut.edu.cn

Supermolecular Interactions in Magnesium-Tin Layered Double Hydroxides

YAO Ping, NI Zhe-Ming, XU Qian, MAO Jiang-Hong, LIU Xiao-Ming, WANG Qiao-Qiao   

  1. Laboratory of Advanced Catalytic Materials, College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, P. R. China
  • Received:2009-06-01 Revised:2009-11-01 Published:2009-12-29
  • Contact: NI Zhe-Ming E-mail:jchx@zjut.edu.cn

摘要:

通过构建镁锡水滑石(Mg3Sn-LDHs-yH2O)周期性计算模型, 基于密度泛函理论, 用CASTEP程序模块, 进行模型的几何全优化. 对各体系的结构参数、Mulliken电荷布居、态密度(DOS)、逐级水合能等进行分析, 探究客体CO2-3和H2O的分布形态及其与主体层板的超分子作用. 结果表明, [Mg6Sn2(OH)16]4+层间插入客体阴离子CO2-3和水分子后, 主客体间存在着较强的超分子作用力, 主要包括静电和氢键作用, 且氢键作用在水合过程中起主导作用, 总体上层板-水(L-W)型/层板-阴离子(L-A)型氢键强度要强于阴离子-水(A-W)型/水-水(W-W)型氢键. 随着层间水分子的增多, 层间距先增大后又稍降低. 当y=0、1时, 客体所在的平面与主体层板平行, 且与两层板的距离基本相等; 当y=2、3时, 客体以偏向某一层板的形式存在. 与层间H2O相比, 层间阴离子CO2-3对体系态密度的影响更显著, 层板与CO2-3的总体作用力大于与H2O的总体作用力. 随着水分子数的增加, Mg3Sn-LDHs-yH2O体系的逐级水合能绝对值逐渐降低, 说明Mg3Sn-LDHs的水合程度不会无限增加, 而是具有饱和量.

关键词: 密度泛函理论, 水滑石, 超分子作用, 逐级水合能, 态密度

Abstract:

We proposed a periodic interaction model for the magnesium-tin layered double hydroxides, Mg3Sn-LDHs-yH2O. Based on density functional theory, the geometry of Mg3Sn-LDHs-yH2O was optimized using the CASTEP program. The distribution of CO2-3 and H2O in the interlayer and the supermolecular interaction between host and guest was investigated by analyzing the geometric parameters, charge populations, density of states, and stepwise hydration energies. Results showed that when CO2-3 and H2O were inserted into the layers of [Mg6Sn2(OH)16]4+, there were strong supermolecular interactions between the host layer and the guests, including hydrogen-bonding and electrostatic interactions. Hydrogen-bonding was superior to the electrostatic interaction in the hydration process. In general, layer-water (L-W) type and layer-anion (L-A) type hydrogen bonding were stronger than anion-water (A-W) type and water-water (W-W) type hydrogen bonding. In Mg3Sn-LDHs-yH2O (y=0-3), the interlayer distance increased then decreased slightly with an increase in the number of interlayer water molecules. At y=0 or 1, the plane of CO2-3 and water was parallel to that of the layer and they were approximately in the middle of the two layers. At y=2 or 3, the guests were not parallel to the host layer and their distribution was random. The impact of CO2-3 was more significant than that of H2O on the density of states of the system. Therefore, the interaction between the layer and CO2-3 was stronger than that between the layer and H2O. The absolute value for the hydration energy decreased gradually with an increase in the number of water molecules. This indicated that the hydration of Mg3Sn-LDHs reached a definite saturation state.

Key words: Density functional theory, Layered double hydroxides, Supermolecular interaction, Stepwise hydration energy, Density of state

MSC2000: 

  • O641