Preparation Of Covalent Organic Frameworks And Studies On Their Sensor And Catalytic Properties

Covalent organic framework materials?COFs?are a class of organic crystalline porous polymers that connected rigid organic building units through covalent bonds.COFs materials are widely used in gas adsorption and storage,catalysis,sensing,energy storage and optoelectronic devices due to their high specific surface area,low density and easy functionalization.In the design of COFs materials,the precise control of COFs pore structure and spatial arrangement can be achieved by the reasonable selection of construction unit and topological structure.In this paper,we also choose some interesting building units to design several COFs with special spatial arrangement,and focus on their applications in sensing and electrocatalysis.The specific work is as follows:In the second chapter,using a salt-mediated synthesis method that a novel porous 2D COF?COF-TFADTH?containing a large amount of hydroxyl groups in the pores was synthesized by thecondensationreactionof2,5-dihydroxyterephthalohydrazide?DTH?and1,3,5-triformylphloroglucinol?Tp?.According to the protonation of amino group in acidic environment and the deprotonation of hydroxyl group in alkaline environment,COF-TpDTH is designed as a highly sensitive pH ratiometric fluorescence sensor.Fluorescence emission showed that the intensity ratio I_{500 nm}/I_{417 nm} of COF-TpDTH increased linearly with pH when the pH was6.3-8.3,which showed high detection sensitivity to near-neutral pH.At the same time,different forms of COF-TpDTH?cations?COF?+1??,neutral?COF?0??and anions?COF?-1???corresponds to different fluorescence emission in different pH?4.0-12.0?environments.On this Basis,we constructed a particularly simple molecular arithmetic system capable of performing semi-subtractive algebraic operations that can be reset after each individual arithmetic step.In addition,COF-TpDTH is also designed as a simple and economical paper-based device for detecting acidic gases and anti-counterfeiting.In the third chapter,using a low-cost mechanochemical?MC?synthesis method that a novel mechanochromic luminescent 2D COF?COF-TpMA?MC??was synthesized by the condensation reaction of 1,3,5-trimethyllocinol?Tp?and melamine?MA?.And the mechanical chromotropic luminescence characteristic of COF-TpMA was explored.It was found that the fluorescence of the monomer mixture?Tp and MA?shifted from⁴75 nm?0 h grinding?to⁵70 nm?grinding 12 h?during the synthesis process,at which time COF-TpMA with bright yellow fluorescence was obtained.After grinding the synthesized COF-TpMA?MC?for 12 hours,the fluorescence quenching of COF-TpMA?MC?was carried out.It is shown that the strong mechanical action will destroy the interlayer interaction and electronic transmission channels,and make COF-TpMA?MC?exhibit the characteristics of mechanochromic luminescence.COF-TpMA?MC??12 h grinding?was designed as a sensor for detecting·OH,which exhibits high sensitivity and accuracy.It has been applied to bioimaging and monitoring of·OH changes in living cells.In the fourth chapter,using a solvothermal synthesis method that two novel 2D COF?COF-TFADTH and COF-TFATH?was prepared by Schiff base aldehyde-amine condensation reaction of tris?4-formylphenyl?amine?TFA?with 2,5-dihydroxyterephthalate diterpene?DTH?and terephthalic acid diterpene?TH?.The effect of electron donor on the catalytic performance of COF materials was studied for the first time.It was found that the COF-TFADTH with electron-donating hydroxyl group had better catalytic performance,which showed that the introduction of electron-donating group could change the electronic structure of COFs,reduce the band gap energy and improve the catalytic efficiency.After doping acetylene black,the catalytic performance of COF-TFATH and COF-TFADTH is greatly improved,indicating that increasing the conductivity of the material can effectively improve the catalytic performance of the COF material.