| Popis: |
The recent increase in use of layered inorganic/organic hybrid materials as solid base catalysts, novel composite materials, and pharmaceutics has resulted in considerable interest in the design, synthesis and understanding of these systems. Layered double hydroxides (LDHs) are often used in the preparation of hybrid materials. Environmentally attractive synthetic routes are studied for the synthesis of MgAl-LDHs incorporating a series of organic dicarboxylate anions (malonate, succinate, glutarate and adipate). The reaction conditions are systematically explored to ascertain the effect of acid chain length, Mg source, slurry weight, and layer charge (i.e. Mg/Al ratio). The materials are characterised by powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, infra-red spectroscopy, thermogravimetric analysis, and elemental analysis. The effect of reaction conditions on product purity and morphology are reported. Impurity free organo-LDHs at low slurry weights and Mg/A1 = 2 are observed. Energy minimization and molecular dynamics computer simulations using both classical atomistic theory and ab initio density functional theory (DFT) are used to investigate the reactivity of organo-LDHs. The influence of the LDH layer charge and water content on the photo-reactivity of intercalculated cinnamate molecules is investigated. Qualitative agreements with previously reported experimental results are obtained. DFT is used to understand the previously reported catalytic reactivity in tert-butoxide intercalculated MgAl-LDHs. The computer simulations identity limitations to the mechanism proposed in the literature and suggest an alternative plausible reaction mechanism. |
