Supramolecular Structure Of Asymmetric Center Intercalated LDH And Their Catalytic Properties Supramolecular Structure Of Asymmetric Center Intercalated LDH And Their Catalytic Properties

Asymmetric catalysis has attracted a widespread attention for its outstanding performance on chiral compounds production. Immobilization is an effective method for the reuse and separation of asymmetric catalyst from reaction system. The interlayer space of layered double hydroxide (LDH) has the characteristic supramolecular structure which can afford the flexible microenvironment for asymmetric center. Therefore, this work focuses on the assembly and structure of chiral ligand in the LDH interlayer, which then are applied to asymmetric catalysis. The main research findings and conclusions include:1. In the preparation of pristine LDH, stacking fault and3R1polytype LDH have been obtained by using different methods which have different pH fluctuation. A ammonium bicarbonate method has been applied to synthesis of3R1LDH, the decomposition of magnesium bicarbonate is the key step. In the tartrate intercalation process, the different intermediate crystalline phases have been observed, the flat orientation tartrate in the LDH gallery for stacking fault LDH and second staging phase of tartrate and carbonate for3R1LDH. The pure second staging LDH has been obtained by the deintercalation of interlayer tartrate with carbonate.2. Titanium cation has been chelated by tartrate in the LDH interlayer gallery, which has the same gallery height and orientation turnover behavior with tartrate LDH. The tartrate titanium complex LDH has been applied to asymmetric epoxidation of cinnamyl alcohol, which shows the low catalytic activity and enantiomeric selectivity.3. Ni(Ⅱ)/Ti(Ⅳ) carbonate layered double hydroxide with high crystallinity has been synthesized by high supersaturation method. The formation process of Ni-Ti-LDH is explained by dissolution-crystallization mechanism, the substitution of Ti (Ⅳ) for Ni (Ⅱ) in the layer decreases the thermal stability of the resulting LDH materials. Ni-Ti-LDH intercalated by tartrate shows less catalytic activity in asymmetric epoxidation of cinnamyl alcohol.4. The reconstruction method has been proven to be an effective means of achieving intercalation of L-proline anions into LDH which shows high optial stability and thermal stability. Applying L-Pro LDH in the aldol reaction reveals that it has no adverse effect on the catalytic activity of L-proline, which has good yield (90%) and high enantiomeric excess (94%). High proline intercalation ratio, low interlayer water content and polar solvent benefit the reaction.