Synthesis Of Azine-linked COFs And Their Fluorescent Properties

Due to their unique structures and excellent performances,such as uniform channels,designable structures,low densities,big specific surface areas,good crystallity,high thermal and chemical stability,covalent organic frameworks(COFs)have been widely applied in many fields including gas storage and separation,catalysis,drug delivery,extraction,chemical sensing and so on.Especially,two-dimensional COFs materials with large ?-bond conjugate structure have stimulated more and more interests for their important application potential in photoelectric transformation and fluorescent sensing.Therefore,to design and synthesize 2-D fluorescent COFs materials specifically recognizing heavy metal ions or toxic small organic molecules is very necessary.In this thesis,four kinks of new 2-D COFs materials based on pyrene structural unit have been successfully synthesized using solvothermal method and characterized by Flourier transformation infrared spectroscopy(FT-IR),powder X-ray diffractometry(PXRD),X-ray photoelectron spectroscopy(XPS),N₂adsorption-desorption experiment and scanning electron microscopy(SEM).Due to large conjugate structure,all of the obtained materialsshowed excellent fluorescence properties.By exploiting the enhancement or quenching of the COFs luminescence by some metal ions or small organic moleculesthese target analytes were successfully recognized and detected by fluorimetry.This thesis consists of five parts as follows:Part I:The design principles,preparation methods and applications of the COFs materials were introduced and the application advances of 2-D COFs materials in fluorescence sensing were reviewed in detail.Part II:Using 1,3,6,8-tetra(4-formylphenyl)pyrene(TFPPy)and thioaminourea(TSC)as raw materials,a novel COF material linked by imine bond(TSC-PyCOF)was successfully synthesized.This material showed a rod-like morphology with burrs,had a big specific surface area and high thermal stability and could emitted strong blue fluorescence.BET surface area was 382.2761 m²/g,mean pore sizes were 7.3(?)and 9.3(?),and the maximum emission wavelength?em=486.5 nm.By employing sensitization of Hg²⁺a new fluorimetric anlysis method for Hg²⁺was developed with a detection limit(DL)down to 0.018?M.And based on the fluorescence quenching property,phloroglucinol was successfully determined with a DL of 0.041?M.Part III:Selecting TFPPy and benzidine(BZ)as reaction monomers,a new COF material,BZ-PyCOF,with strong fluorescence performance was prepared.This sheet-like crystalline COF material possessed a micropor and mesopore composition structure,big specific surface area and good thermal stability.BET surface area was182.3341 m²/g and mean pore sizes were 13.67(?)and 21.59(?).The results showed that Fe²⁺could strongly quench the luminescence of BZ-PyCOF dimethyl sulfoxidesolution,which might be used in sensitive and selective determination of Fe²⁺with a DL of 0.012?M.Part IV:With TFPPy and 2,6-diaminoanthraquinone(DT)as building units,a new COF material,named as DT-PY COF,was synthesized.The prepared material displayed a uniform spherical morphology,had a good crystallity,relatively big specific area and high thermal stability and could emitted strong blue fluorescence with?em=455.7 nm.It was applied in quantitative determination of Cr³⁺by fluorescence quenching method.Part V:By choosing TFPPY and 2,6-diaminopyridine(DP)as monoers a new COF material,DP-PyCOF,was prepared.The COF material showed a loosely distributedfusiform morphology with an average pore size of 11(?).Based the strong quenching effect of Fe³⁺for DP-PyCOF lumicescence,a sensitive fluorescent assay method for Fe³⁺was proposed.