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Synthesis And Fluorescence Application Of Imine Two-dimensional Covalent Organic Frames

Posted on:2024-05-28Degree:MasterType:Thesis
Country:ChinaCandidate:Y L LiFull Text:PDF
GTID:2531307061967619Subject:Materials science
Abstract/Summary:PDF Full Text Request
Covalent organic framework(COFs)materials are a newly emerging class of organic crystalline porous materials that prepare a network porous structure with light elements(such as C,H,O,N,B,etc.)through topological structure presetting.They are of great application in various fields such as catalysis,optoelectronic storage,electronic components,gas adsorption,and chemical sensing.In particular,by functionalizing the structure of COFs and applying them to the field of fluorescence sensing,smaller molecular fluorescence probes have larger specific surface area and porosity,additional reaction units,and are conducive to enhancing their identification performance,which has attracted much attention from researchers.This article synthesized three types of COFs fluorescent probes(TTP-COF,TAP-COF,SFP-COF)through the design and modification of COFs for the recognition and adsorption of metal ions and the detection of H2S in aqueous solutions.The contents of this paper are summarized in the following three sections,1)Two dimensional imino porous covalent organic frameworks(TTP-COF and TTF-COF)were designed and synthesized from 1,3,5-tris(4-aminophenyl)benzene(TAPB),2,4,6-triformyl phloroglucinol(TP)and promote aldehyde(TF),respectively.By simulating the structure of these two COFs using Materials Studio(MS),the XRD images obtained were compared with the experimental XRD images,and it was found that the data had significant overlap.At the same time,the analysis results of Fourier transform infrared spectroscopy(FT-IR)can support the successful preparation of TTP-COF and TTF-COF.Both TTP-COF and TTF-COF have large specific surface areas(578.05 m2·g-1and 719.2 m2·g-1)and microporous properties(0.74 nm and0.72 nm).Through fluorescence performance analysis,it was found that TTP-COF has specific recognition performance and elevated recognition sensitivity(LOD=10 n M)for Cu2+.The fluorescence mechanism of TTP-COF is studied by DFT calculation:the intramolecular hydrogen bond between C=N and-OH groups causes the excited state intramolecular proton transfer(ESIPT)effect,which leads to the generation of fluorescence.After the addition of Cu2+,specific coordination with the C=N and-OH groups occurs,hindering the ESIPT effect and leading to fluorescence quenching.The probe can reach a peak adsorption capacity of 214 mg·g-1(p H=6)at room temperature and has strong reusability(>5 cycles).The development of this probe provides a potential tool for the detection and adsorption of Cu2+.2)A two-dimensional imino porous covalent organic framework(TAP-COF)was designed and synthesized with tri(4-aminophenyl)amine(TAPA)and 2,4,6-triformyl phloroglucinol(TP)as precursors.The successful synthesis of TAP-COF is confirmed by the comparison of FT-IR results and XRD data obtained from MS simulations with experimental measurements.TAP-COF has excellent thermal stability,with a mass loss of less than 15%within 50-440℃.The fluorescence performance shows that it has specific recognition performance for Cu2+,and there is a excellent linear relationship between ion concentration and fluorescence intensity(R2=0.9942).In the range of 2-10μM,the linear equation is y=674434-8920.35x.Using DFT calculations,it was demonstrated that the addition of Cu2+inhibits the ESIPT effect through coordination with the-OH and C=N groups,leading to fluorescence quenching.In addition,the probe can reach a strong adsorption capacity of 229.42 mg·g-1(p H=6)at room temperature and has elevated reliability(>5 cycles).3)Based on the selectivity of thiophene ester to H2S,the precursor 2,5-bis(thiophenoyloxy)-terephthalic acid dicarbohydrazide(SF-3)was synthesized from 2,5-dihydroxy-1,4-diethyl terephthalate as the starting material through three steps of esterification,substitution reaction and amidation,and then a novel covalent organic framework SFP-COF was prepared by solvothermal synthesis with 2,4,6-triforyl phloroglucinol(TP).The probe has a relatively large specific surface area(1169.1 m2·g-1)and microporous characteristics(pore size 0.6911 nm).Research has shown that SFP-COF exhibits significant fluorescence enhancement in H2S,with a lower detection limit(LOD=20 n M)and superior selectivity.The mechanism of fluorescence identification was investigated by DFT calculations.H2S attacks the thiophenyl group,removing the protective group,and exhibits fluorescence enhancement.The preparation of SFP-COF provides a novel design strategy for the qualitative and quantitative detection of H2S.
Keywords/Search Tags:Covalent Organic Framework(COF), Cu2+, recognition, ESIPT, adsorbent, H2S
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