Design And Synthesis Of Chiral Porous Metal-organic Materials For Asymmetric Catalysis

Metal-Organic Porous Materials have attracted extensive attention for their varieties of aesthetically interesting structures and great interests for applications in a number of fields.The study of chiral metal-organic porous catalytic materials has profound significance for improving the activity and enantioselectivity of chiral catalysts,especially for improving the efficiency of catalysts.In this paper,chiral Zr schiff base MOFs,chiral schiff base metal-organic cage and chiral MOFs nanosheets were constructed by coordination self-assembly.The structure and composition of these materials were characterized by single crystal X-ray diffraction and other characterization methods,and their applications in asymmetric catalysis were further explored based on their respective characteristics.This paper is divided into five chapters:In Chapter 1,the synthesis and recent development of chiral metal-organic porous materials were introduced in detail.The emphasis is given to the characteristics and research progress of chiral metal-organic porous frameworks(CMOFs),two-dimensional MOFs nano-sheet(NAs)and metal-organic cages in the field of asymmetric catalysis.The challenges and opportunities remained in this area,and overviews of the thesis topic and progress were discussed and presented.In Chapter 2,highly stable metal-organic frameworks(MOFs)with potentially acid-labile chiral catalysts were synthesized via postsynthetic exchange.Through a one-or two-step ligand exchange,a series of asymmetric metallosalen catalysts with the same or different metal centers are incorporated into a Zr-based Ui O-68 MOF to form single-and mixed-M(salen)linker crystals(Ui O-68-M).The chiral MOF catalysts are highly enantioselective and completely heterogeneous and can be recycled after extracting the product and reused for at least ten times without obvious loss of activity and enantioselectivity,making them attractive catalysts for eco-friendly synthesis of fine chemicals.This work not only advances Ui O-type MOFs as a new platform for heterogeneous asymmetric catalysis in a variety of syntheses,but also provides an attractive strategy for designing robust and versatile heterogeneous catalysts.In chapter 3,Ultrathin chiral two-dimensional nano-sheets(NAs-1 ~ NAs-3)based on chiral BINOL/BIPHENOL MOFs(MOF-1 ~ MOF-3)were obtained by ultrasonic exfoliation.The NAs maintains the original coordination structure of MOFs but with about 1.5 ~ 9.0 nm thickness.Due to the easy access to exposed active sites and fast mass transfer within the ultrathin layers,the NAs are shown to be efficient and recyclable asymmetric catalysts for intramolecular amidation of imines.And this work for the first time explored the asymmetric catalytic properties of NAs,providing new ideas for the construction of chiral catalysts with high activity and high enantioselectivity.In Chapter 4,a chiral octahedral Metal-Organic Cage(MOC-1)were constructed by using twelve enantiopure Mn(salen)-derived dicarboxylic acids as linear linkers and six Zn4-p-tert-butylsulfonylcalix[4]arene clusters as tetravalent four-connected vertices.The porous cage features a large hydrophobic cavity(~3944 (?)3)decorated with catalytically active metallosalen species and is shown to be an efficient and recyclable asymmetric catalyst for the oxidative kinetic resolution of racemic secondary alcohols and the epoxidation of olefins with up to > 99% ee.The cage architecture not only prevents intermolecular deactivation and stabilizes the Mn(salen)catalysts but also encapsulates substrates and concentrates reactants in the cavity,resulting in enhanced reactivities and enantioselectivities relative to the free metallosalen catalyst.In Chapter 5,a briefly conclusion and prospects were given.