Density Functional Theory Investigating Interlayer Structure and Ion-Exchange Properties of Mg/Al Layered Double Hydroxides

The two-sheets model was proposed to investigate interlayer structure and properties of Mg/Al layered double hydroxides (LDHs) containing F-, Cl-, Br-, I- and OH- using density functional theory (DFT). The results show that four types of halogen anions in the interlayer of LDHs have the same configurations due to simple sphere structures of isolated anions. As the size of halide anions increasing, the interlayer spacing dc increase. Mulliken charge analysis illustrates that the host layers interact with the guest anions by the electrostatic interaction and hydrogen bonding, and the charge transfers from anions to layers. The frontier orbital of the host layer interacts with that of the guest anions, and the electron transfers from HOMO of anions to LUMO of the host layer. Moreover, the order in the absolute value of binding energy is: OH- >F- >Cl- >Br- >I-, that remains consistent with ion-exchange ability of LDHs reported.