Super-Molecular Interaction between Cl− and H2O within the Restricted Space of Layered Double Hydroxides

A periodical interaction model of LDHs-Cl-yH2O has been proposed. The geometry optimization and energy of the layered double hydroxides (LDHs) were calculated using CASTEP/LDA method at the CA-PZ level. The distribution of H2O in the interlayer and the super-molecular interaction between host layer and guest anion have been investigated by analyzing the geometric parameters, charge population, energy, and density of state (DOS). The results showed that there was a strong super-molecular interaction between the host layer and the guest anion Cl−. In the system of LDHs-Cl-yH2O, the interlayer distance increased gradually then tended to invariableness. And in the process of hydration of LDHs-Cl, hydrogen bonding was superior to electrostatic interaction, and layer-water type hydrogen bonding was a little stronger than anion-water type hydrogen bonding between H2O and the rest of the structure. When y was 1 or 2, Cl− and the plane of water were parallel to the layer; while y was 3 or 4, distribution of Cl− and water was random. Moreover, the LDHs-Cl-yH2O would change from ionic crystal to molecular crystal with the increase of number of water molecule. The hydration of LDHs-Cl would achieve a definite saturation state.