Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (08): 1869-1876.doi: 10.3866/PKU.WHXB201205212

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Influence of Interlayer Water Content on Supermolecular Interaction of Copper-Iron Layered Double Hydroxides

SHI Wei, HU Jun, NI Zhe-Ming, LI Yuan, LIU Jiao   

  1. Laboratory of Advanced Catalytic Materials, College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, P. R. China
  • Received:2012-01-20 Revised:2012-05-21 Published:2012-07-10
  • Contact: NI Zhe-Ming E-mail:jchx@zjut.edu.cn

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Abstract:

A periodic interaction model was proposed for the copper-iron layered double hydroxides, Cu3Fe-LDHs-yH2O(y=0-2). Based on density functional theory, the geometry of Cu3Fe-LDHs-yH2O was optimized using the CASTEP program. The distribution of NO3- and H2O in the interlayer and the supermolecular interaction between host and guest was investigated by analyzing the geometric parameters, hydrogen-bonding, charge populations and stepwise hydration energy. Results showed that when NO3- and H2O were inserted into the layers of Cu3Fe-LDHs, there was strong supramolecular interaction between the host layer and the guest, including hydrogen-bonding and electrostatic interaction. Hydrogen-bonding was superior to the electrostatic interaction in the hydration process. The strength of hydrogen bonding was Layer-Anion(L-A) type hydrogen bonding＞Anion-Water(A-W) type hydrogen bonding＞L-A type hydrogen bonding＞Layer-Water(L-W) hydrogen bonding＞ Water-Water(W-W) type hydrogen bonding. In Cu3Fe-LDHs-yH2O, the interlayer distance decreased slightly and then increased significantly with an increase in the number of interlayer water molecules. The Cu-O octahedral forms were stretched gradually, because the Jahn-Teller effect of Cu2+ increased. The absolute value for the hydration energy decreased gradually with an increase in the number of water molecules. This suggested that the hydration of Cu3Fe-LDHs reached a definite saturation state. The geometry parameters of Cu3Fe-LDHs-1H2O is close to the ideal hexagonal, the metal distortion of layer is the weakest and the stability is the strongest, interlayer distance matchs with the experimental value, so the Cu3Fe-LDHs-1H2O is a stable configuration.

Key words: Density functional theory, Copper-iron layered double hydroxides, Supramolecular interaction, Jahn-Teller effect, Stepwise hydration energy