The Preparation And Characterization Of Cu(?)-Functionalized SBA-15 Silicas And Its Application In Organic Catalysis

SBA-15 is a kind of highly ordered mesoporous silica materials,which has been widely used in the fields of catalysis,separation,biomedicines and materials science.It processes many attractive features,such as uniform open-framework structure,thick wall of the hole,high hydrothermal stability,large specific surface area,controllable pore size and so on.Although pure SBA-15 silicas were found few applications in catalysis,they have been widely used as carriers for many organic catalysts.In this thesis,we loaded Cu(?)onto the surface of carboxylic acid-modified SBA-15 to obtain Cu(?)-functionalized SBA-15 silica(SBA-15-PTAA-Cu(?))by post-grafting method and then applied it as a solid Cu(?)catalyst in organic synthesis.The contents were as follows:Part 1.The catalyst SBA-15-PTAA-Cu(?)was prepared in three steps.First,the surface of SBA-15 silica was grafted with 3-(2-(tert-butoxycarbonyl)ethylthio)propyl groups by refluxing of pre-synthesized SBA-15 with silicane coupling reagent tert-butyl 2-(3-(trimethoxysilyl)propylthio)acetate in toluene,then the tert-butyl ester was hydrolyzed by H₃PO₃ in toluene to form corresponding carboxylic acid.After that,the resulted carboxylic acid groups grafted on the surface of SBA-15 were utilized as chelating group to coordinate Cu(?)to afford SBA-15-PTAA-Cu(?).In addition,a wide range of technologies,including XRD,TEM,BET,IR,TGA,AAS,UV-Vis,XAFS and so on,were used to characterize all the intermediates and SBA-15-PTAA-Cu(?).The results showed that the structure of SBA-15-PTAA-Cu(?)was similar to parent SBA-15,with pore size of 5.1 nm,surface areas of 431 m²/g and pore volumes of 0.59 cm³/g.Moreover,the content of copper(II)in SBA-15-PTAA-Cu(?)was found to be 1.26 mmol/g.Part 2.The catalytic activity of SBA-15-PTAA-Cu(?)was investigated in the Chan-Lam cross-coupling reaction of arylboronic acids and sodium azide.The results showed that by using 6 mol%of SBA-15-PTAA-Cu(?)as catalyst and under air condition,a wide range of substituted arylboronic acids could selectively be converted to corresponding aryl azides in Me OH at room temperature.Unfortunately,we found that a large amount of aryl azides are high volatile,thus a majority of these aryl azides were isolated in lower yields.Part 3.The catalytic activity of SBA-15-PTAA-Cu(?)was investigated in the Click reaction of benzyl azides and terminal alkynes.The results showed that under N₂ atmosphere and by using 3 mol%of catalyst,0.8 eqivalent of ascorbic acid(based on Cu(?)of the SBA-15-PTAA-Cu(?))as a reducing agent,both benzyl azide and phenyl azide could smoothly react with a wide range of aromatic and aliphatic terminal alkynes with sole region-selectivity,and the corresponding product1,4-disubstituted 1,2,3-triazols were isolated in 90%-97%yields.Part 4.The catalytic activity of SBA-15-PTAA-Cu(?)was investigated in the two-step cascade reaction of arylboronic acids,sodium azide and terminal alkynes in one-pot process.Firstly,aryl azides were obtained under the same conditions as described in Part 2.After that 1 m L of water,0.8 eq.of sodium ascorbate(based on Cu(?)of the SBA-15-PTAA-Cu(?))and the terminal alkynes were added successively,followed by equipped with a balloon of N₂.Finally,a wide range of1,4-disubstituted 1,2,3-triazoles were obtained in 65%-98%yields.Noteworthy,in all above reactions,the catalyst SBA-15-PTAA-Cu(?)could be easily recovered by simple filtration and washed with organic solvents.It was found that the recovered catalyst could be reused for at least more than 4 times without any obvious loss of catalysis activity,which showed it has high stability under above reaction conditions and is an excellent heterogeneous Cu(?)catalyst.