| Single-Atom Catalysts(S ACs)refers to the catalysts in which the active metal components are dispersed in the form of a single atom.Compared to traditional nano-catalysts,SACs often show high activity,high selectivity in organic catalysis owing to the maximum efficiency of atom-utilization and unique structure properties.Up to now,there have a few studies on MOFs-based SACs,but,to the best of our knowledge,there has no any report on isolated single vanadium site catalysts derived from amino-functionalized MOFs.Based on the properties of MOF material NH2-MIL-101 with vanadium(V)as metal centers,in this master’s thesis,isolated single vanadium site catalysts(V-N-C-x,x stands for the pyrolysis temperature)were prepared by a high temperature pyrolysis followed with acid leaching strategy.The physicochemical properties of NH2-MIL-101(V)and V-N-C-x were systematically characterized by X-ray diffraction(XRD),N2 adsorption,X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM),transmission electron microscopy(TEM),and X-ray absorption spectroscopy(XAS)techniqures.It is established by those characterizations that the metal active component is present as a single atom in the catalysts.The CO2 adsorption properties of the NH2-MIL-101(V)materials were measured under ambient conditions.The catalytic properties of the derived V-N-C-x catalysts were evaluated in the selective oxidation of sulfides and the "one-pot" synthesis of 2-arylquinazoline via oxidative dehydrogenation,respectively.The main results are summarized as the follows:(1)Based on the synthesis method reported in the literature and our experience for the synthesis of the analogue NH2-MIL-101(Fe)(change the reactor,reduce the synthesis temperature and adjust the Raw material consumption).We modified the method for the synthesis of amino-functionalized MIL-101(V)material.Through the fully characterizations,it is demonstrated synthesized NH2-MIL-101(V)has a large specific surface area and a high crystallinity.The single component gas adsorption isotherms of CO2 and N2 by V-MOFs at 273 K、288 K and 298 K was measured by static volume method.The results show that NH2-MIL-101(V)shows high adsorption capacity for CO2.Its excellent adsorption performance is mainly attributed to the amino group on the NH2-MIL-101(V)skeleton,which is easy to interact with CO2.(2)Single metal vanadium site catalyst(V-N-C-x)was derivated by a pyrolysis-acid leaching strategy using NH2-MIL-101(V)as sacrifice template.Under mild reaction conditions(40℃,1.5 eq TBHP),V-N-C-600 can efficiently catalyze the oxidation of sulfides to sulfoxides.Through the substrate expansion experiment,the universality of V-N-C-600 in the selective oxidation of sulfides is demonstrated.Compared to V-C-600 and traditional V2O5 catalysts,the prepared V-N-C-600 catalysts showed higher catalytic activity.After being reused for 6 times,the catalytic activity did not decrease significantly,and the structure and composition of the catalyst did not change.Its excellent catalytic performance is mainly attributed to the high dispersion of the active sites in the V-N-C-600 catalyst,which makes the catalytic active sites fully exposed.(3)Quinazoline compounds have a wide range of applications in the fields of medicine and pesticides.Therefore,the developed V-N-C-600 catalyst was further applied to the one-pot synthesis of 2-Aryl-quinazolines by catalytic oxidative dehydrogenation reaction.Under the optimized conditions,V-N-C-600 can efficiently catalyze the conversion of 2-aminobenzylamines and aromatic aldehydes to 2-Aryl-quinazolines.The highly dispersed active site can efficiently promote the dehydrogenation of the intermediate 2-Aryl-1,2,3,4-tetrahydroquinazolines.High specific surface area and porous structure might beneficit for the improvement of full contact of reactants,thus boosting the catalytic performances.The results showed that SACs is a promising candidate for applications in organic synthesis. |
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