Theoretical investigation on the structure of anions intercalated MgAl-layered double hydroxides and the interaction between anions and host layer

The structure of anion-intercalated MgAl-layered double hydroxides (MgAl-LDHs) and the interaction between the anion and host layer were investigated by density functional theory (DFT); the anions considered were inorganic ones like F^-, Cl^-, NO₃^-, CO₃^2- and SO₄^2-, as well as organic ones like p-(CH₃)₂N(C₆H₄)COO^-, (C₆H₅)COO^-, HO(C₆H₄)COO^-, C₁₂H₂₅SO₃^-, C₆H₁₃SO₃^- and C₃H₇SO₃^-. The geometric structures and interactional energies between the anions and host layer were obtained. The results showed that there is a strong supra-molecular interaction between anions and host layer of MgAl-LDHs and the interactional energy values followed the orders of CO₃^2- > SO₄^2- > F^- > Cl^- > NO₃^-, p-(CH₃)₂N(C₆H₄)COO^- > (C₆H₅)COO^- > HO(C₆H₄)COO^-, and C₁₂H₂₅SO₃^- > C₆H₁₃SO₃^- > C₃H₇SO₃^-. In addition, the interaction mechanism between anions and host layer was considered by the natural bond orbital (NBO) analysis; the trend of stability energies calculated by the second order perturbation agrees well with that of the interactional energies.