Synthesis of Metal Organic Coordination Polymers and Their Catalytic Behavior

Author:Zhang Xiao Fei

Supervisor:tang zhi yong liu shao qin

Database:Doctor

Degree Year:2019

Download:52

Pages:151

Size:6645K

Keyword:

Metal-organic coordination polymers are three-dimensional porous materials,which are self-assembled by metal ions and organic ligands.The metal ions with different valence states and different organic ligands enable the design and synthesis of tunable functional materials.They have the characteristics of high stability,easy recovery from solution and could exhibit superior performance in the fields of catalysis,energy,separation,and drug delivery.Therefore,design and construction new coordination polymers at molecular level have become effective strategy and means to enhance catalytic performance.This thesis mainly includes the formation of Cu-POMOF by loading catalytic active heteropolyacid;controlling the morphology of Ni-BDC and Co-Pc through increasing the interlayer spacing of the layered polymers or adding surfactants;regulating the difference in the coordination environment of UiO-66.The specific research contents are as follows:A novel metal organic coordination polymer Cu-POMOF has been successfully synthesized under hydrothermal conditions by adding heteropolyacid H5PMo10V2O40·14H2O,CuCl2·2H2O and 1,2,4-triazole.The single crystal structure of Cu-POMOF has been successfully prepared and analyzed by adjusting the growth conditions.Cu-POMOF could catalyze oxidation of cyclohexane at 100°C under ambient pressure with the yield of 23%.The products,cyclohexanol and cyclohexanone,commonly known as KA oil,are important chemical industries for the production of nylon-6 and nylon-66.The analysis of single crystal structure and X-ray absorption spectrum analysis of synchrotron radiation show that the coordination of unsaturated tetravalent vanadium in Cu-POMOF participates in the activation of H2O2,which in turn forms a vanadium oxygen double bond transition state.The heteropolyacid functionalized metal-organic coordination polymer has good stability and can effectively prevent the catalytic active component from being lost into solution.Ni-BDC metal organic coordination polymer nanosheet with thickness of only about 1.5 nm has been obtained by adding surfactant polyvinylpyrrolidone.The two-dimensional material obtained by limiting longitudinal growth of the metal-organic coordination polymer can expose more active sites and could catalyze conversion of citronellal and malononitrile at room temperature with the yield of98%,which shows better catalytic performance compared with bulk Ni-BDC metal organic coordination polymers.Co-Pc metal organic coordination polymer nanosheet with thickness of 4-5 nm obtained by cobalt tetraaminophthalocyanine and 2,5-di-tert-butyl-1,4-benzoquinone under ultrasonic assisted synthesis.Compared with the commonly terephthalaldehyde,2,5-di-tert-butyl-1,4-benzoquinone can increase the interlayer spacing of polymers to a certain extent,weaken the interaction force between the layers,and thus can facilitate ultrasonic assisted stripping.Further,in order to show universality of this method.another two polymer nanosheets can be obtained by reacting tris(4-aminophenyl)benzene and tris(4-aminophenyl)amine with2,5-di-tert-butyl-1,4-benzoquinone.Since cobalt phthalocyanine has a certain Lewis acidity and could catalyze conversion of propylene oxide into cyclic carbonates with the yield of 99%.Synchrotron radiation X-ray absorption spectroscopy studies have found that Co-Pc metal-organic coordination polymer nanosheets can expose more catalytic active sites under same condition and have stronger Lewis acidity than bulk materials,which can activate reactant molecules efficiently.A series of structurally adjustable UiO-66 metal organic coordination polymer are synthesized by adding different sizes of organic ligands such as formic acid and trifluoroacetic,Zr metal centers of synthesized UiO-66 have different coordination structures,and the metal coordination polymers formed by formic acid could catalyze the reduction of ethyl levulinate toγ-valerolactone at 150°C with the yield of 99%.Through experimental analysis,it is found that the difference in catalytic activity lies in the difference in the spatial chemical structure around the Lewis acid active center.The larger the space around the Lewis acid active center,the more favorable for formation of the intermediate cyclic transition state.At the same time,combined with the density functional theory(DFT)calculation,it is found that the formic acid regulated UiO-66 reduces the energy of forming cyclic transition state about 15.16 kcal/mol compared with polymer containing only terephthalic acid.Last but not least,controlled experiments further elaborates the intrinsic relationship between its catalytic activity and its structure.