Chiral Macrocycles-Based Covalent Organic Frameworks:Design,Synthesis,and Application

Chiral macrocycles occupied inherently confined cavities,excellent host-guest bonding properties,and unique physical and chemical characteristics,widely applied in supramolecular chemistry,functional materials,life science,information science and other fields.The construction of novel chiral macrocycles-based porous materials is one of the frontier scientific issues in the field of supramolecular macrocycles.Covalent organic frameworks(COFs)are a novel type of crystalline organic porous materials.With the advantages of long-range order structure,high specific surface area,and tailored functionalities,COFs have been widely applied in gas storage,catalysis,separation and other fields.The design and synthesis of chiral covalent organic frameworks remains a considerable challenge.Chiral macrocycles are critical building blocks for chiral materials.The introduction of chiral supramolecular macrocycles into COFs would not only effectively solve the shortage of macrocycles,such as low specific surface area and difficult recovery,but also make macrocyclic units disperse evenly in COFs,improving the application performance and usage efficiency of materials.However,as far as we known,chiral macrocycles-based covalent organic frameworks were rarely reported.This thesis focuses on two topics:the design,synthesis,and application of novel chiral macrocycles,and chiral macrocycle-based covalent organic frameworks.The major works were summarized as follows:(1)The synthesis of novel norbornane-based chiral macrocycles,and their chiral recognition properties research.A new type of chiral macrocycles,(all-R)-1 and(all-S)-1,were facilely synthesized from norbornane building blocks.The synthesis process was monitored by mass spectrometry,revealing the precisely construction of[2+2]macrocycle in the reaction.As evidenced by NMR spectroscopic analysis,the enantiomer of pharmaceutical drugs and intermediates(G1–G7)have been effectively recognized by(all-R)-1 and(all-S)-1.The chemical shift differences(ΔΔδ)could reach 0.128 ppm.Thence,norbornane-based chiral macrocycles with excellent chiral recognition abilities have been efficiently synthesized.(2)Characterization of the host-guest interaction between norbornane macrocycles and guests.Investigation the structural factors affecting the chiral recognition abilities of norbornol macrocycles.Host-guest binding model between norbornane-based chiral macrocycles and guests was characterized by ~1H NMR titration experiments and single crystal X-ray diffraction.The single crystal structure of host-guest complex of(all-R)-1 and(S)-G1intuitively revealed that G1 was embedded within the macrocyclic cavity of(all-R)-1via four strong hydrogen bonds,which was defined as quadruply hydrogen bonding model.The novel binding model only reveals the chiral recognition mechanism of norbornane macrocycle,but also proved that norbornane units and macrocyclic structure are the key factors for the superior chiral recognition properties of norbornane macrocycles.(3)The construction of chiral supramolecular macrocycles-based covalent organic frameworks via“bottom-up”strategy.Three chiral amide macrocycles-based building blocks were designed and synthesized.Using the chiral amide macrocycles as functional building blocks,a series of chiral amide macrocycle-based covalent organic frameworks(M-COFs)were successfully constructed.Their structures were characterized by PXRD,ss NMR,IR,BET,thermogravimetric,SEM.With the different chiral environments,pore sizes,and optical properties,M-COFs provided material library for the applications research of COFs.(4)The application research of chiral macrocycle-based covalent organic frameworks(M-COFs).In view of the superior host-guest properties of supramolecular macrocycles,M-COFs was applied in chiral recognition and chiral resolution.As the result,M-COF-4 could recognize the enantiomer of chiral amine,alcohol and acid.The enantiomeric fluorescence difference ratio(ef value)for 1-methylbenzylamine could reach 1.5.While used in chiral solid phase extraction,enantioselective adsorption of ibuprofen was given by M-COF-1 with 8%ee value,and 1,1′-bi-2,2′-naphthol by M-COF-1 with 11%ee value.