Characterization, synthesis and catalysis of hydrotalcite-related materials for highly efficient materials transformations

This review is intended to introduce recent progress in the characterization, synthesis and catalysis of hydrotalcite (HT) and HT-related materials. NMR, in situ neutron diffraction and TG-DTA techniques have been used to determine the local structure and structural changes of HT. Various synthetic methods of controlling the morphology of HT are introduced together with the crystal formation mechanism. The preparation methods of magnetic HTs are also included. The HT acts as a heterogeneous base catalyst for efficient transformations of organic compounds such as the synthesis of glycerol carbonate, transesterification of oils (biodiesel production) and carbon-carbon bond formations. The HT has also been used as a support for immobilizing various metal species (Ru, Pd, Ag, Au, Pt, Cu, V, Mn etc.), which enables highly selective organic reactions such as dehydrogenation of alcohols and deoxygenation of epoxides. Cooperative actions between basic sites of the HT surface and supported metal species are introduced. It is also shown that the HT can work together with other solid acids and metal catalysts to promote sequential reactions in a one-pot manner, which gives us a very important methodology for environmentally-benign synthesis of value-added chemicals, especially from biomass-derived compounds.