Fluorescence Regulation And Application Of Luminescent Covalent Organic Framework Materials

Covalent organic frameworks（COFs）is a new type of crystalline porous material,which has the advantages of adjustable pores,easy functionalization,orderly pore structure and large specific surface area.COFs have become a promising organic luminescent material.The molecular components,topological structures and functional groups on the pore wall can affect the intrinsic electronic and photophysical properties of COFs.Therefore,this thesis focuses on"fluorescence regulation and application of luminescent covalent organic framework（LCOFs）",a series of LCOFs with different emission were synthesized,the fluorescence characteristics of LCOFs were regulated by different strategies,and different application designs were carried out.The main work is as follows:（1）Regulate fluorescence of 1,3,5-tris（phenylacetylene）benzene-based covalent organic framework.Herein,five kinds of 1,3,5-tris（phenylacetylene）phenyl LCOFs were synthesized by changing the connection mode,topological structure and substituent.The introduction of 1,3,5-tris（phenylacetylene）benzene skeleton improved theπ-conjugation of LCOFs and enlarged the frameworks of LCOFs.The COF_BTTH-TDprepared by using terephthalic dihydrazide（TD）as linker and 1,3,5-tris（phenylacetylene）benzene skeleton（BTTH）emitted green light.The 1,3,5-tris（phenylacetylene）benzene skeleton containing tert-butyl reacted with different degrees of conjugation with melamine,TD,hydrazine hydrate and p-phenylenediamine to obtain LCOFs emitted blue,yellow,orange and red luminescence colors,respectively.According to the three primary color matching formula,two or three kinds of 1,3,5-tris（phenylacetylene）benzene-based LCOFs were mixed to achieve white emission,which was used for white light-emitting diodes and information encryption and decryption.The work provides a simple and efficient method to edit the emission behaviors of LCOFs systematically.（2）Fluorescence regulation of hydrazone linkage covalent organic framework for real-time visualization field determination of norfloxacin.Fluorescence regulation of hydrazone linkage COF for real-time visualization field determination of norfloxacin（NOR）.Four kinds of hydrazine linked COFs(COF_BMTH-TFB（blue）,COF_BMTH-TB（yellow-green）,COF_BMTH-TBT（yellow）and COF_BMTH-HB（orange）)with different luminescent colors were prepared by using 2,5-bis（2-methoxyethoxy）terephthaloylhydrazine as the core and aldehyde monomers containing hydrogen,methoxy and different numbers of hydroxyl groups as the connecting units.These functional groups can be used as sites to trigger variousπ-electron effects,including resonance,hyperconjugation and tautomerism,to change the electronic structure of the framework and further achieve precise regulation of the emission wavelength of LCOFs.In addition,the fluorescence sensor of NOR can be constructed by combining the inherent blue emission of NOR with different emitting LCOFs.Based on the obvious color change in the detection process,a real-time detection tool combining test paper and App of smartphone was designed,which successfully realized the monitoring of NOR in real fish samples.This portable paper sensor reduces the dependence on traditional instruments and provides data support and theoretical support for rapid and simple visual detection of NOR.（3）A“turn on”fluorescent sensor based on multi-variable covalent organic framework for ultra trace water detection.A series of TFPT_[X]-BMTH-COFs（X=0、33、50、67、100）with aggregation-induced emission（AIE）properties were synthesized by Schiff base reaction using 2,5-bis（2-methoxyethoxy）terephthalhydrazide（BMTH）,1,3,5-tris（4-formylphenyl）benzene（TFPB）and 2,4,6-tris（4-formylphenyl）-1,3,5-triazine（TFPT）as precursors.By adjusting the content of TFPT component in TFPT_[X]-BMTH-COFs,the degree of intramolecular charge transfer（ICT）and AIE properties can be effectively adjusted,and the relative effect of water on the fluorescence of the system can be changed.Among them,TFPT_[67]-BMTH-COF has the weakest degree of ICT.When a small amount of water appears in organic solvents,the fluorescence enhancement caused by AIE is significantly stronger than the fluorescence weakening caused by ICT.Compared with other three-component COFs,the fluorescence enhancement effect is the most obvious,and the detection limit is as low as 0.00007wt%,realizing the detection of ultra-trace water in DMF.By depositing TFPT_[67]-BMTH-COF on filter paper,on-site visual detection of trace water was realized.In addition,the water-induced DMF sensitive rapid change method was also applied to detect the content of water in food sample.