| Polyoxometalates?POMs?,with their versatile structural topologies,nucleophilic oxygen-enriched surface,strong acidity and oxidbillity,unique"pseudo-liquid phase"reaction field,represent one of the excellent candidates for the development of heterogenous catalysis.Keggin-type POMs and their derivatives are a typical POM,which have different structures and composition.Metal-organic framework?MOFs?as hybrid solids with infinite networks display their potential applications in many areas for their readily fine-tuned channels or pores by changing the ratio of metal ions and organic bridged ligands.Thus,the targeted functions could be achieved in an accurate manner.More importantly,a variety of catalytic centers such as chiral groups and inorganic groups can also be directly introduced in MOFs,giving them different properties and functions from each component,and showing a synergistic effect.Combined the redoxcatalyst POMs with the functional MOFs through hydrothermal synthesis,a series of POMOFs with different structures were assembled.In POMOFs,POMs acting as a template can not only induce metal ions and organic ligands to form nanoporous material,but also increase the stability of MOFs,which make POMOFs have a broad application prospect in catalysis.In this paper,a series of POMOFs({Co6-Zn5W19},{Fe-Zn5W19-BPY},{Co-SiW11-DPNDI},{Fe-SiW11-DPNDI},NH2-Co-PYI1 and NH2-Co-PYI2)were designed and synthesized by hydrothermal synthesis.Sandwich type[WZn3?H2O?3(ZnW9O34)2]12–,trivacancy?-keggin POMs[?-SiW9O34]10–and Keggin type polyacid anion[CoW12O40]6– were introduced as precursors with the combination of different functional ligands and transition metal ions,respectively.Their stability and purity have been demonstrated by the basic characterizations and performance tests.In addition,the catalytic properties of some compounds were studied.In chapter one,sandwich-type Na12[WZn3?H2O?2(ZnW9O34)2]·48H2O was selected as precursor and reacted with rigid organic ligand 4,4'-bpy and metal salt Co?NO3?2·6H2O or FeSO4·7H2O under hydrothermal conditions.Two new porous complexes of [Co?H2O?6]2{[Co?H2O?4]4 [WZn3?H2O?2(ZnW9O34)2]}·8H2O {Co6-Zn5W19} and [Fe?bpy??H2O?]2[Fe?bpy??H2O?4]2 [WZn3?H2O?2(ZnW9O34)2]·4H2O{Fe-Zn5W19-BPY} were obtained,respectively.They were characterized by elemental analysis,infrared spectroscopy,thermogravimetry,X-ray powder diffraction and X-ray single crystal diffraction to verify the basic properties of the compounds such as purity and stability.In addition,the application of {Co6-Zn5W19} in the catalytic oxidation of Bayer-villiger?BV? was further studied.Through the optimization of reaction conditions and control experiments,the results showed that {Co6-Zn5W19} as heterogeneous catalyst has good catalytic activity and high selectivity in the oxidation of ketones.The catalytic activity remained almost the same when it was recycled and reused for 5 runs.In chapter two,by combination of?-Keggin POMs [?-SiW9O34]10–,Co?II?/Fe?II? and photoactive organic ligands DPNDI,a pair of isomorphic Sandwich-type POMOFs [Co2?DPNI?][Co?H2O?4]2[Co?DPNI??H2O?4?CH3CN?][(Co4SiW11O40)2]·8H2O {Co-SiW11-DPNDI} and [Fe2?DPNI?][Fe?H2O?4]2[Fe?DPNI??H2O?4?CH3CN?][(Fe4SiW11O40)2]·8H2O {Fe-SiW11-DPNDI} were prepared under hydrothermal method.A series of structural characterizations were verified to the stability and the purity of samples such as IR,PXRD,TG and so on.Taking {Co-SiW11-DPNDI} as the research object,the photocatalytic reduction and cycloaddition of CO2 were studied owing to its structural stability,intermolecular interaction,"two centers" catalytic sites and low potential etc.The experimental results showed that {Co-SiW11-DPNDI} has good catalytic activity and chemical selectivity under mild conditions such as low temperature,low pressure and without any co-catalyst.The catalytic activity can be recycled and reused for many times.In chapter 3,by simultaneously introducing Lewis acid and Lewis basic into a polyoxometalate based metal-organic framework,a pair of enantiomer [Co2?NH2-BPY?2?HPYI?2?H2O??CH3CN?][CoW12O40]?NH2-Co-PYI1 and NH2-Co-PYI2? were achieved and characterized by IR,PXRD,CD,TGA.NH2-Co-PYIs displayed high catalytic activity and selectivity in synergic catalysis Aldol/Knoevenagel condensation as bifunctional catalysts.Multiple catalytic active sites were orderly distributed and spatial matching,which would be a powerful approach to increase the stability and the corresponding functions and to enhance their reactivity through a synergistic cooperation between different catalysis sites. |
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