Acta Phys. -Chim. Sin. ›› 2010, Vol. 26 ›› Issue (01): 175-182.doi: 10.3866/PKU.WHXB20100111


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


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


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