Design, Assembly And Chiral Separation Properties Of Chiral Coordination Porous Materials Based On Chiral Amino Acid

Porous coordination materials are a class of crystalline organic-inorganic hybrid functional materials with porous structure constructed from organic ligands and metal ions（clusters）by coordination.Because of their large porosity and easy regulation of structure and function,this type of porous materials has attracted much attention of scientists in various fields such as gas adsorption,drug delivery,catalysis and separation.In particular,porous coordination materials with homochirality have become a research hot due to their potential applications in the fields of asymmetric catalysis and chiral separation.However,long synthetic route,expensive chiral source and complicated preparation have limited the development of homochiral porous materials and thus porous coordination structures with high-efficiency chiral resolution performance are still rare.In this thesis,amino acid was used as the skeleton,and three kinds of chiral bridged ligands with different structures were designed and synthesized by simple organic reaction.Then a series of porous coordination molecular cages and metal-organic framework materials were constructed and fully characterized by single and powder X-ray diffraction,IR,UV,TGA,FL and so on.In addition,the performance of such materials in chiral resolution of racemic small molecules,for example epoxides and aromatic alcohols,was studied.The thesis can be divided into five chapters,which are as follows:In the second chapter,a chiral bridging ligand H₃L1 with C₃ symmetry was designed by using four-step reaction with L-phenylalanine as the chiral source,and them,two isomorphic octahedral double-layer coordination molecular cages PCC-57and PCC-60 with uniform chirality were constructed with the lanthanide metal ions La³⁺and Nd³⁺.The structures of the coordination molecule cages were studied by X-ray single crystal diffraction and other techniques.In view of their unique chiral cavity structure,they are capable of efficiently separating racemic epoxy compounds and aromatic alcohol compounds with an ee value of up to 99.5%,and the coordination molecule cage can be recycled five times and the performance is maintained without loss.In the third chapter,tryptophan was used as the initial chiral source,and another chiral bridging ligand H₃L2 with C₃ symmetry was synthesized by four-step reaction.Then,two octahedral coordination molecular cages were prepared by solvothermal reaction of H₃L1 and H₃L2,respectively,with metallic copper ions.Among the two cages,the L-phenylalanine-based octahedral coordination cage can selectively separatingɑ-phenylethyl alcohol,and the ee value is as high as 99%,while the L-tryptophan-based octahedral coordination cage is also separatingɑ-phenylethanol,but with a low ee value of 39%.The difference in the selective separation ofɑ-phenylethanol by these two coordination molecule cages may be due to the difference in chiral environment of the coordination molecule cage.In the fourth chapter,a chiral bridging ligand H₂L3 with C₂ symmetry was designed and synthesized by four-step organic reaction with L-phenylalanine as the chiral source.A two-dimensional metal-organic framework material was prepared by the reaction of metal zinc ions with H₂L3 under the assistant of 4,4’-bipyridine,which is confirmed by various techniques such as X-ray single crystal diffraction.In addition,the porous material is capable of efficiently separating racemic aromatic alcohols with an ee value of up to 99%,and the ee value is still as high as 95%after three recycles.