Preparation, Characterization And Catalytic Performance Of Functionalized PMOs Materials

Periodic mesoporous organosilicas(PMOs)with organic moiety bridging in the framework have attracted great interest because of the combined advantages of inorganic-organic composites and mesoporous structure.The uniformly distributed organic moieties in the mesoporous framework will impart the PMOs the possibility of tailoring the pore structure,framework composition,and morphologies over a wide range,which make them exhibit many potential applications in separation technology(chromatography,membranes,etc.), catalysis,nanoelectronics,sensors,etc.The properties of the PMOs mainly depend on the properteies of the brigeds organic moieties in the framework.At present,only several limited bridged organosilane precursors, (R-O)₃Si-R-Si(OR-)₃,can be employed for synthesis of PMOs with high organic content,high order and high structure stability,which greatly limit the modification and application of PMOs.To solve the problem,new preparation method is very desirable.Based on above background,in this thesis,several kinds of functionalized PMOs were prepared by new methods and their physical properties and catalytic performance were investigated in detail.It is expected that the above research can provide theoretical and practical basis for the design and development of new hybrid material and new heterogeneous catalysts.The main research contents in this thesis are as follows:1.PMOs have been synthesized by hydrothermal method and were characterized by XRD,N₂ adsorption.The influence of the amount of water, acid concentraction,crystallization time,crystallization temperature on the synthesis of PMOs were investigated and obtained the optimized synthesis conditions.2.Organotin functionalized PMOs(OrSn-PMOs)were prepared by three different methods and their physical properties and catalysis performance in direct synthesis of DMC for CO₂ and methanol were investigated.Firstly, OrSn-PMOs were prepared by post synthesis grafting(MeO)₂ClSi(CH₂)₃SnCl₃ on PMOs with different amount of BTEB;secondly,tOrSn-PMOs were prepared by co-condensation of TEOS and BTEB with(MeO)₂ClSi(CH₂)₃SnCl₃ using P123 as a structure-directing agent under acdic conditions;thirdly, OrSn-PMOs were prepared by cloromethylation of bridged phenyl moieties in the framework of PMOs,then reacting with SnCl₂ through Grignard reaction. The prepred samples were characterized by XRD,N₂-adsorption,UV-vis and elemental analysis.The results showed that organotin could be successfully grafted on PMOs by three different methods.All the samples exhibit higher catalytic activity in direct synthesis of DMC for CO₂ and methanol than the corresponding homogeneous catalyst,and the activity increase with the increase of the organic moieties in the framework in the PMOs.3.PMOs functionalized with metal Rusalen and Mnsalen(Msalen-PMOs) were prepared by cloromethylation of phenyl moieties in the framework of PMOs,and a serial of organic reactions occurred on the formed phenmethyl and their catalytic performance in cyclohexene oxidation were investigated.XRD, N₂-adsorption,UV-vis and elemental analysis results showed that Msalen can be effectively grafted on PMOs by this method and the ordering of the mesoporous material were maintened.Further,compared with the corresponding Msalen-SBA-15 prepared by the similar grafting method,the Msalen-PMOs have higher complex loading.In cyclohexene oxidation,the prepared Msalen-PMOs were not only more active and selective for epoxide,but also exhibit higher stability than the corresponding Msalen-SBA-15.