Research On Synthesis And Properties Of Fluorescent Covalent Organic Polymers

There are a lot of environmental problems in the process of industrial development and production activities,such as cationic/anionic pollution,explosive analogue pollution,organic matter pollution,antibiotic pollution,energy waste（such as the use of mercury lamp）,etc.,which will bring huge adverse effects on people’s health,environmental/social safety and other fields.Efficient and rapid detection of pollutants is of great significance to life safety and green ecology.Although the detection of advanced instruments and equipment has the characteristics of high selectivity,the disadvantages of high detection cost,limited operating environment and slow response limit their application scope.Fluorescence detection method has the advantages of high selectivity,low detection limit,fast response,easy operation,high recovery,anti-interference and so on.The development of novel fluorescent materials with high selectivity is of great significance for the detection of environmental pollutants.And organic fluorescent materials generally have high quantum efficiency,which can solve the problem of energy waste caused by mercury lamp.Covalent organic polymers（COPs）have many advantages,such as low relative density,large specific surface area,controllable function and so on.They have been widely used in fluorescence sensing,gas adsorption,drug carrier,photocatalysis and so on.COPs with fluorescent properties can be used as fluorescent probes for the detection of cations/anions,volatile organic compounds,explosive analogues and antibiotics due to its porous,stable and high cycling.In this paper,a series of covalent organic polymers（COPs）with fluorescence properties were designed and synthesized,and their applications in fluorescence sensing detection of cation/anion,explosive analogues,antibiotics,recognition of volatile organic compounds with different sizes and solid-state luminescence were studied.The main contents and innovations of this paper are as follows:（1）Two covalent organic polymers（COP-1,COP-2）with high fluorescence properties were prepared by using tetrastyrene（TPE）with AIE properties as the core building unit.This two COPs have the great performance in detecting Fe³⁺,the selectivity is better than the control cations(Li⁺,Na⁺,K⁺,Mg²⁺,Ca²⁺,Ba²⁺,Yb³⁺,Er³⁺,Eu³⁺,Sm³⁺,Pr³⁺,Cr³⁺,Cd²⁺,Zn²⁺,Mn²⁺,Ni²⁺,Co²⁺,Cu²⁺);the detection limits of the two polymers to detect Fe³⁺are0.42μM and 0.89μM,respectively.The fluorescence quantum efficiency of COP-1 and COP-2 is 18%and 16.5%,respectively.As a yellow phosphor with high quantum efficiency,white LED with excellent CIE coordinate was successfully assembled with commercial blue LED,the coordinate values are COP-1（0.32,033）and COP-2（0.31,0.32）;COP-2 has good chemical sensing effect for permanganate（Mn O₄^-）and TNP,the selectivity is better than that of common anions(NO₃^-,Cl O₄^-,HCO₃^-,Cl^-,SO₄^2-,PO₄^3-,S₂O₇^2-,S₂O₈^2-,I^-,SO₃^2-,OH^-)and explosives analogues（NB,1,2-DNB,1,3-DNB,2,6-DNT）;The detection limits of COP-2 for Mn O₄^-and TNP are 2.17·10^-3 m M and 0.0067 ppm,respectively.It not only provides a new fluorescence sensing platform for the field of chemical sensing,but also provides a new possibility for the preparation of white LED.（2）Two novel covalent organic polymers（COP-3 and COP-DPATPE）were prepared by the reaction of TPE with two different fluorescent molecules（DPA,Pyrene）through Suzuki coupling reaction.COP-3 and COP-DPATPA both have aggregation induced emission（AIE）phenomenons;And for volatile organic compounds sensing,they showed“turn on”effect with the increase of analyte molecular size.Chemical sensing experiments show that the LOD（0.191μM）of COP-3 for Fe³⁺ions is the lowest in the reports of covalent organic polymer.And COP-DPATPE has the detection limit of 1.44μM for Fe³⁺ions,which are superior to the corresponding national testing standards.The selectivity of COP-3 and COP-DPATPE for Fe³⁺ions is better than that of the control cations(Li⁺,Na⁺,K⁺,Mg²⁺,Ca²⁺,Ba²⁺,Er³⁺,Eu³⁺,Pr³⁺,Cr³⁺,Cd²⁺,Zn²⁺,Mn²⁺,Ni²⁺,Co²⁺,Cu²⁺).The selective expression ability of COP-DPATPE for TNP is significantly better than that of NB,1,2-DNB,1,3-DNB and 1,4-DNB;And the detection limit of COP-DPATPE for TNP is18.89 ppb.Excellent detection performance provides theoretical support for the practical application of materials.（3）We adopt diphenylacetylene（DPA）and tribromobenzene（TBB）,diphenylacetylene（DPA）and 4,4’-Dibromotriphenylamine（TPA）as monomers to synthesize the new fluorescence COPs（COP-DPAT,COP-DPATPA）.COP-DPAAT and COP-DPATPA can detect ferrous ion(Fe²⁺)well in the presence of Zn²⁺,Pb²⁺,Ni²⁺,Cd²⁺,Cu²⁺,Co²⁺and other interfering ions.The quenching constants of COP-DPAT and COP-DPATPA for ferrous ion detection are 0.0271μM^-1 and 0.011μM^-1,respectively.The newly fluorescent COPs provide a new idea for the detection of iron element in the environment;In addition,both COPs have very good fluorescence quenching phenomenon for TNT,the results show that the quenching percentage can still reach above 90%under the interference of NB,1,2-DNB,1,3-DNB and 1,4-DNB;And the COP-DPATPA was successfully used to prepare the test paper for TNT detection,which provides an experimental basis for the practical detection of this kind of materials.（4）We adopt pyrene-2,7-diboronic Acid Bis（pinacol）Ester（PDABE）and TBB,PDABE and 4,4’-Dibromodiphenyl sulfoxide（BSF）as monomers to synthesize COP-TP and COP-FP,respectively.COP-TP has the selective ability to detect Fe³⁺ions,whereas COP-FP has the great performance in sensing Hg²⁺ions.The quenching constant of COP-FP for mercury detection is 0.1347μM^-1,and that of COP-TP for iron detection is0.2561μM^-1.And good cycling and anti-interference ability confirmed the excellent performance of the material.COP-FP has a certain detection ability for NB,TNP,2,6-DTP,and the addition of 2,6-DTP will make the fluorescence quenching percentage of COP-FP reach 98.5%.It is found that COP-TP has a very good selective quenching effect for levofloxacin,and the selectivity of COP-TP for levofloxacin is better than that of roxithromycin,ampicillin,epifloxacin,etc.The corresponding quenching constant of levofloxacin is 0.0258 ppm^-1.The research provides more possibilities for the detection of fluorescent organic polymer materials.