Structural change from homogenous structure to staging in benzoic acid intercalated LDH: experimental and molecular dynamics simulation insights

The intercalation the of 4,4'-oxybis(benzoic acid) anion (OBA(2-)) into MgAl-layered double hydroxide (LDH) was carried out in formamide, and the structural change of the nanocomposites from homogenous to staging was investigated through in situ XRD, FT-IR, TG-DSC, SEM and molecular dynamics (MD) simulations. In both formamide and water, the nanocomposites had a homogenous structure with a basal spacing of ～1.7 nm, showing the configuration of OBA(2-) was vertical to the LDH layers; however, with a decrease in water content after drying, the structure changed to a staging with a basal spacing of 2.62 nm. This resulted from the 1.72 nm phase and another one of 0.85 nm, which was produced by the configuration of OBA(2-) horizontal to the LDH layers. MD simulations revealed that the LDH layers distorted surrounding OBA(2-), and the deformation became more severe with decreasing water content in the interlayer, leading to the staging formation. The simulated XRD pattern confirmed that the staging observed in the experimental pattern was of the Daumas-Hérold type.