Preparation,Characterization And Analytical Application Of Covalent Organic Frameworks Based On 1,3,5-tris(4-formylphenyl)benzene

The synthesis and application of porous organic framework polymers have flourished in recent years.They are a kind of new porous polymer material with microporous or mesoporous structure linked by chemical bond of organic structural units,mainlu including porous aromatic frameworks?PAFs?,metal organic frameworks?MOFs?and covalent organic frameworks?COFs?and so on.Covalent organic frameworks?COFs?,constructed by the organic structural units only consisting of some light elements such as carbon,hydrogen,oxygen,nitrogen and boron etc.through thermodynamics reversible reaction,are a kind of crystalline microporous polymers with uniform pore channel.So they are usually called“organic molecular sieve”.Due to many remarkable merits,for example,highly ordered and adjustable aperture,high specific surface area,low density,good thermal and chemical stabilities,various synthesis methods,easily functionalization and so on,these materials have widely used in many fields including gas storage and separation,optoelectronic applications,catalysis,proton conduction,drug delivery,fluorescence sensing and so on.In this thesis,a series of imine bond-linked covalent organic framework polymers with large?-conjugated structure and uniform pore size were designed and synthesized by using 1,3,5-tris?4-formylphenyl?benzene as the essential building unit.Their structures and properties wer characterized by FT-IR,XPS,XRD,TGA,SEM and N₂ sorption-desorption experiment in detail.In the meantime,their fluorescence properties and related applications for metal ion detection were investigated in detail.The thesis consisted of our parts as follows:?1?A novel imine based covalent organic framework?TFPB-COF-1?was synthesized from benzidine and 1,3,5-tris?4-formylphenyl?benzene?TFPB?,which was prepared by the reaction of 1,3,5-tribromobenzene and 4-formylphenylboronic acid,and benzidine via Schiff base reaction using a solvothermal method.This COF could emit strong blue fluorescence under ultraviolet excitation with a maximum emission wavelength?_em=400 nm.It was found that Fe²⁺and Fe³⁺ions could strongly quench its luminescence and the decreased fluorescence intensity had a good linear relationship with the concentration of the metal ions,so that it could be employed for selective and sensitive determination of Fe²⁺and Fe³⁺.?2?By microwave assisted Schiff base reaction of TFPB and p-phenylenediamine a new COF material TFPB-COF-2 were prepared.This COF material possesses a strong blue fluorescent emission at?_em=464 nm when excited at ultraviolet light.A novel turn-off mode fluorescence analytical strategy for sensitive detection of Mn²⁺was developed based on its strong quenching effect for the COF fluorescence.?3?Using TFPB and 2,6-diaminopyridine as building monomers a new imine bond-linked COF?TFPB-COF-3?was synthesized through a solvothermal procedure.by exploiting strong quenching property of Ag⁺ion for this COF luminescence,a rapid,sensitive and selective analytical method for Ag⁺was proposed.?4?A hydrazine bond-linked COF?N₀-COF?with a bright blue-purple fluorescent emission was successfully synthesized via an one-pot method with TFPB and hydrazine hydrate as monomers.The experiment results demonstrated that Fe³⁺showed strong quenching property,while Mn²⁺displayed strong increasement for this COF fluorescence emission.Based on these characteristics,a turn-on mode fluorimetric analytical method for Mn²⁺and a turn-off mode analytical method for Fe³⁺were developed.The proposed methods possessed high sensitivity,quick response and good selectivity.