Functional Design Of Covalent Organic Framework Hybrid Materials:Luminescence And Sensing Studies

In this thesis,functionalized covalent organic framework（COFs）hybrids were used as research objects,and luminescent motifs were introduced into the COFs through in situ synthesis and postsynthetic modification（PSM）.The luminescence regulation of COFs by luminescent motifs was systematically studied,the photophysical properties of COFs hybrid materials were explored,as well as the preliminary applications of the hybrid materials in the detection of drugs,volatile organic compounds（VOCs）,metal cations and biomarker sensing.Quantitative analysis of drugs.Eu³⁺functionalized COFs（TpPa-1）hybrid material Eu@TpPa-1 was first developed as a highly selective fluorescent switch for the detection of antibiotic levofloxacin in serum and urine.TpPa-1 acts as a host matrix providing protection for the introduced Eu³⁺.Eu³⁺acts as a bridge in the overall detection system,exerting its characteristic emission.The determination of levofloxacin in the range of high and low concentrations was achieved.Next,a hybrid material EB-TFP:Eu（BTA）₄ of rare earth anion complex（Eu（BTA）₄^-）and COFs（EB-TFP）was designed and synthesized.It is a sensing platform for the ratiometric fluorescence detection of the anticancer drug 5-fluorouracil（5FU）,enabling the rapid preparation of two-dimensional（2D）COFs nanosheets（NSs）（<10 min）.The interaction exist between 5FU and COFs hybrid materials,the interlayerπ-πstacking of COFs is weakened,facilitating the exfoliation of the native COFs to obtain COFs NSs.Detection of volatile organic compounds.COFs（TpPa-1）achieved a fluorescence turn-on response to triethylamine（TEA）vapour during deprotonation with good sensitivity and reproducibility.The prefabricated detector provides a viable method for detecting TEA at the ppm level and can alert people to take timely action to reduce the environmental hazards caused by TEA.The designed and synthesized imine COFs（TtDFP）emitting green fluorescence.It functionalized with Eu³⁺emitting red fluorescence.The obtained hybrid material Eu³⁺@TtDFP can be further assembled into a portable sensor.It can be used as a smart nose to distinguish and detect three VOCs related with Huanglongbing（HLB）.Sensing analysis of biomarkers.COFs（TpPa-1）was first functionalized with a sodium fluorescein dye to synthesize the hybrid material TpPa-1@Dye.TpPa-1@Dye is an indicator for the indicator displacement assay（IDA）-in-COFs system,while Cr³⁺is an electron-deficient group（which can be used as a cross-linking agent for sodium alginate in the preparation of hydrogels）.Cr³⁺is an analyte sialic acid（SA,a biomarker for the diagnosis of ovarian cancer）receptor.The interaction between TpPa-1@Dye and Cr³⁺caused fluorescence quenching.Since SA can displace the interaction between TpPa-1@Dye and Cr³⁺to trigger the emission of dye.Fluorescence TpPa-1@Dye hydrogel could monitor ultrasensitive（ppb-level）SA for the diagnosis of ovarian cancer.Secondly,the fluorescent sensor TpPa-1@LE,constructed from the products of TpPa-1 and TEA,allows the quantitative detection of methylglyoxal（MGO）,a biomarker used in the diagnosis of diabetes mellitus in serum.Quantitative detection of multiple analytes.The functional hybrid material Eu₄W₈@EB-TFP was first generated by polyoxometalate（POM,Eu₄W₈）in situ growing in the skeletal aperture of COFs（EB-TFP）.This material combines the advantages of POM and COFs;endows COFs with excellent luminescence properties and effectively broadens the sensing applications of COFs.Eu₄W₈@EB-TFP can be used as a sensitive chemical sensor to monitor trace amounts of Ag⁺in the environment as well as cholyglycine（CG,a biomarker for liver cancer cells）in biological systems.Secondly,a two-step PSM strategy for COFs（Tp BD-（OH）₂）gets hybrid material Tp BD-（COOH）₂@Eu TTA,with excellent luminescence properties and good structural stability.The further prepared hydrogel can be applied for the detection of two validated indicators relevant to the diagnosis of Parkinson’s disease（PD）,namely homovanillic acid（HVA）and Al³⁺.The fluorescent sensor exhibits a fluorescence quenching response for HVA and a ratiometric recognition method for Al³⁺.Simultaneous quantification of the two indicators can greatly improve the accuracy of PD diagnosis.In this paper,we have done a lot of exploratory work in constructing hybrid materials using COFs,which fully demonstrate the advantages and potential applications of COFs in constructing hybrid materials.