Synthesis,Characterization And Catalytic Properties Of Amphiphilic Hollow Porous Nanomaterials Supported Rh Nanoparticles

In the past few decades,large areas of lakes and oceans have suffered chemical pollution.Environmental issues have received close attention in industry and life,and it is the general trend to seek safer,greener and more sustainable chemical reaction conditions.However,in organic reactions,the compatibility between organics and water is poor,and the reaction intermediates are easily affected by the strong nucleophilicity of water,which results in most of the reaction efficiency is not optimistic,making most organic reaction processes emphasize anhydrous systems.In fact,using water as a solvent,low temperature,low pressure,low toxicity,non-combustibility and non-explosion are ideal reaction conditions in organic reactions.Water is the most promising green solvent,which is incomparable with widely used organic solvents such as methylene chloride.Based on this,it is necessary to design a solid catalyst that uses water as a solvent for the reaction.The traditional hydroreduction reaction was carried out at high temperature in an autoclave,which was usually accompanied by huge risks and toxic flammable solvents.Although transfer hydrogenation provides an attractive alternative route for the reduction of nitroaromatics,where hydrazine was used as a reducing agent,the cytotoxicity of hydrazine was a technical and economic challenge.In this dissertation,by modifying the structure of amphiphilic mesoporous silicon materials,we explore the green catalytic efficiency and selectivity of materials for reducing nitroaromatic hydrocarbons under mild conditions.In the second chapter,polybenzoxazine spheres?PB?were prepared by the methods reported in the literature,then nanospheres PB@SiO₂ coated with mesoporous silica shells were prepared by adding a silicon source tetraethyl orthosilicate.Calcined in an inert atmosphere at high temperature,the internal PB spheres were carbonized from the inside to the outside.Due to the limitation of the outer shell,the inner polymer was pyrolyzed and even embedded in the shell to form a carbon layer.The carbon shell and internally doped nitrogen fragments constituted the NC@HS nanosphere.The precious metal Rh particles were then loaded by the dip-reduction method to form the final nanosphere Rh/NC@HS.The scanning electron microscope?SEM?,transmission electron microscope?TEM?,powder X-ray diffraction?XRD?,N₂adsorption isotherm,and X-ray photoelectron spectroscopy?XPS?were used to characterize the morphology and structure of the synthesized materials.The doped nitrogen fragments enhanced the interaction between Rh and the nanospheres.At the same time,the silica support can effectively prevent the aggregation and leaching of metal particles during the reaction process,so that the nanospheres still had good stability when boiled at high temperature for 48 hoursIn Chapter 3,we took the reduction reaction of nitroaromatics as the research object,and aimed at green catalysis.By adjusting the material itself,the reaction temperature,substrates and other factors to seek high activity and selectivity under mild conditions,at the same time to ensure no pollution to the environment,fewer by-products,safe non-toxic,cheap and efficient green mild conditions.The hydrophobic reactor of nitrogen-doped hollow carbon shell and the hydrophilic reactor formed of silicon spheres were combined to coat precious metal nanoparticles and connect organic reactants with water.Its emulsification improved the reaction performance.This structure made the materials show excellent amphiphilicity.The hydrophilicity of the outer surface allowed these materials to be fully dispersed in water.The internal hollow cavity was hydrophobic so that organic matter can be enriched in the internal cavity for reaction,so it can be catalytically reduced under mild conditions.In this work,an efficient mesoporous hollow silicon nanosphere catalyst was developed,which showed good adsorption and catalytic performance.On this basis,continue to explore the application of hollow double shell nanomaterials in other fields,and strive to exert its maximum value.