Rational Design, Assembly And Properties Of Chiral Framework Materials Based On VO(Salen)

Chiral metal-organic frameworks(MOFs) have become one of hot topics in the field of chemistry and materials, owing to their diverse structures and potential applications in asymmetric catalysis, chiral recognition and separation, enantioselective fluorescent sensors, gas adsorptionand so on. Herein, carboxyl- or pyridyl- functionalized organic linkers based on C2-symmetric VO(Salen) skeletons were synthesized and further utilized to build porous MOF 1 and MOF 2 with robust structures and unique functions. The as-synthesized compounds were characterized by a variety of techniques, such as X-ray diffraction, elemental analysis, thermogravimetric analysis, circular dichroism spectroscopy and so on. Their applications in asymmetric catalysis were also explored. This thesis includes the following three chapters.In Chapter 1, the research background about chiral MOFs is briefly introduced, including their synthesis and applications in asymmetric catalysis,chiral recognition and separation, and chiral sensors. Then the issues and challenges remained in this area were discussed. At last, an overview of the thesis topic and the research progress were presented.In Chapter 2, two C2-symmetric carboxyl- or pyridine- functionalized chiral Salen ligands L1-H4 and L2-H2 were prepared in several steps. After reacted with VO(acac)2, the metalloligands VO(L1-H2) and VO(L2) were got, then VO(L1-H2) was utilized to assemble with Zn I2 to afford a chiral MOF 1. VO(L2) was assembled with diphenyldicarboxylic acid and CdI2 to afford chiral MOF 2. After oxidation, MOF 1a and MOF 2a could be served as efficient heterogeneous catalysts for asymmetric cyanation reaction of aldehydes. As for MOF 1a, the ee is up to 95%ee. The result is better comparing with the homogeneous analogue. And because of the confinement effect, when the catalyst loading is very low, this advantage is more obvious. Because of the differenent structures, when use MOF 2a as catalyst, the highest ee is only 90%. The result is lower than MOF 1a. And both the two materials are very stable, they could be reused for 5 times without significant loss in activity and enantioselectivity. In addition, due to the layer-pillar structure of MOF 2, we used it to do the solvent assisted ligand exchange reaction and got anisomorphic MOF 2b in which the ratio of VO(L2) and Cr(L2) is 3 to 2. Due to the addition of catalytic active site Cr, MOF 2b showed other catalytic property, it can catalyze the reaction of asymmetric aminolysis of aromatic epoxide, and the ee is up to 76%.In Chapter 3, a briefly conclusion and outlook were given.