Synthesis And Application Of Covalent Organic Frameworks Containing Cyclohexanediamine And Amino Acid Chiral Sites

Covalent organic frameworks（COFs）are ordered crystal structures in which organic monomers are joined by covalent bonds.COFs are used in many fields due to their large specific surface area,structural and chemical stability,functional pore walls and adjustable frames.Combining COFs with chiral compounds can construct chiral COFs（CCOFs）,and the resulting CCOFs have significant chiral advantages.At the same time,COFs can be used as heterogeneous catalysts due to their excellent properties,so we have explored the synthesis and application of CCOFs.1.The synthetic methods of chiral covalent organic frameworks（CCOFs）and their progress and application in asymmetric catalysis were summarized.2.We gradually synthesized ZIF-90-（R or S）-NH₂ and core-shell ZIF-90@（R or S）-COFs on the basis of known ZIF-90,and then removed the core ZIF-90 by acetic acid etching template method to obtain Hollow-（R or S）-COFs,and finally loaded Rh Cl₃ on Hollow-（R or S）-COFs by post-modification method,and finally obtained the Rh@Hollow-（R or S）-COFs catalyst.In order to identify its application performance,we selected the asymmetric hydrogenation reaction with acetophenone as the substrate to verify the catalytic effect and stereoselectivity of the chiral shell Rh@Hollow-（R or S）-COFs catalyst,and the results showed that the catalyst had a good catalytic effect on this reaction,with a yield of 99%and an ee value of 96%.Moreover,the catalyst has not reduced its catalytic activity after five cycles,and is a relatively good heterogeneous catalyst.In addition,we also extended the substrate of this asymmetric hydrogenation reaction and found that the catalytic reaction yield of both electron-absorbing and electron-giving substituents was above96%and ee value was above 70%.This shows that the properties and position of the substituents do not affect the reaction effect,and the catalyst has good performance.3.In order to further study and explore the asymmetric catalytic performance of CCOFs,we synthesized monomer L,and then combined the newly synthesized monomer L with trialdehyde group phloroglucinol and L/D-valinic acid to synthesize the chiral L/D-COF catalyst by one-pot method.We demonstrated the successful preparation of chiral L/D-COF by characterizing the chiral L/D-COF by powder diffraction,infrared,scanning electron microscopy,thermogravimetric analysis,gas sorption-resolution experiments,and solid nuclear magnetism.In addition,the catalytic performance and stereoselectivity of the chiral L/D-COF were verified by the asymmetric silicon hydrogen addition reaction of acetophenone.The results show that the catalyst has excellent catalytic performance for the asymmetric silicon hydrogen addition reaction of acetophenone with a yield of 95%and an enantiomer selectivity of about 80%.In addition,the XRD of the catalyst remained intact after five catalytic cycles,and the catalytic activity did not decrease significantly.In addition,we carried out substrate expansion for the asymmetric silicon hydrogen addition reaction of acetophenone,and found that the catalyst still maintained good catalytic activity and stereoselectivity for acetophenone derivatives,which was a good heterogeneous catalyst.