Construction Of Ionic Microenvironment In The Polyacrylonitrile Fiber Surface And Its Adsorption,Catalytic Properties

In recent years,polyacrylonitrile fiber（PANF）has attracted more and more attention due to its unique structure and properties.PANF possesses a large amount of cyano groups and methoxycarbonyl groups and can be easily modified with specific molecules through the amination reaction.It accordingly becomes a popular support materials.In this thesis,the functionalized PANF was prepared by the following steps:the anion and cation microenvironment was constructed in the surface layer of PANF,following by loading phosphotungstic acid or metal nanoparticles through ion exchange or electrostatic interaction.The applications of the functionalized fibers in the forming reactions of C-C bonds and C-N bonds,the reduction of 4-nitrophenol and the removal of dye pollutants were explored.The main research results were shown as follows:1.Various acid functionalized fibers with different pK_avalues were prepared,from which a series of anionic functionalized fibers were prepared through acid-base regulation.Their adsorption properties were systematically studied.The results shows that phenolic anion functionalized PANF(PAN_P（-）F)with the strongest alkaline has the best selective adsorption performance for cationic dyes,it has many advantages such as a wide range of pH values（4～12）,large saturated adsorption(25 ℃,2.306mmol g^-1),high removal rate（99.80%）and low adsorption limit（20 ppb）.Additionally,the BCB concentration can be lowered to 20 ppb in the initial stage of adsorption and remained below 1.69 ppm within 825 minutes adsorption process under a continuous flow condition.2.Different sulfonic acids,sulfamic acid and bisulfate acid-functionalized fibers were prepared,and used as the catalyst in the synthesis of heterocyclic compounds.The results show that the optimal catalyst PAN_EOSF with the strongest acidity can efficiently catalyze Friedlander reaction,the synthesis of quinazolinone and4-1（H）-quinazolinone,and Friedel-Crafts reaction of 4-hydroxycoumarin and aromatic aldehyde in water,with yields as high as 99%,99%,99%and 96%.PAN_EOSF can be reused for 20 times without any decrease of catalytic activity.A protic acid"Release-Catch-Release"catalytic mechanism was proposed.3.The quaternary ammonium functionalized fibers with cationic microenvironment were prepared,from which a series of phosphotungstic acid-functionalized PANFs with strong Br（?）nsted acidity were then prepared by ion exchange.The results show that the phosphatungstic acid functionalized fiber（CAT-12）with the weakest basicity and moderate hydrophobicity has the best catalytic performance.It can efficiently catalyze the synthesis of 4-1（H）-quinazolinone（yield:92～99%）and Friedel-Crafts reaction of indole withβ-nitrostyrene（89～99%）.The system has advantages of low dosage of catalyst,mild reaction condition,usage of non-toxic solvent,and extensive substrate scope.Additionally,a"Catch-Catalyze"catalytic mechanism was proposed.4.Various silver nanoparticle supported quaternary ammonium salt,pyridine salt and imidazole salt functionalized PANFs were prepared.The reduction reaction of4-nitrophenol catalyzed by the fiber catalysts were studied.The results show that the quaternary ammonium salt functionalized fiber-supported Ag（0）nanoparticle catalyst with butyl side chains(PAN_QA-C4F-Ag（0）)has the best catalytic activity,efficiently catalyzing the reduction reaction of 4-nitrophenol at room temperature（conversion rate of 99.6%）with the 4-nitrophenol concentration lowered to 0.38 ppm.Additionally,PAN_QA-C4F-Ag（0）can be reused 20 times without any decrease in catalytic activity（conversion rate of 99.3%）.The reasonable two-phase reaction catalysis mechanism in sight of the cationic microenvironment was proposed.5.Various aza ligands and quaternary ammonium functionalized acrylic fibers were prepared and applied to the preparation of palladium nanoparticle functionalized fibers.The catalytic activities of these catalysts were systematically studied.Among which,the Gemini quaternary ammonium fiber immobilized Pd（0）nanoparticles catalyst PAN_GQAF-Pd（0）exhibited the best catalytic activity.It can effectively catalyze Heck reaction and reduction reaction of 4-nitrophenol with high yield of76～98%and 99%,respectively.The catalyst can tolerate an extensive scope of substrates under mild reaction conditions.PAN_GQAF-Pd（0）is easily recovered,and it can be reused 10 times with little decrease in catalytic activity and low Pd leaching（only 3.69%）.It is noteworthliy that the concentration of 4-NP could be decreased as low as 5 ppb,which is far lower than the maximum contamination level of 2 ppm for nitroaromatics containing wastewater in China.A"release-catch"immobilization mechanism was proposed...