Nanostructured Porous Functional Materials:Design,Synthesis And Applications In Amphiphilicity And Catalysis

In the past few years,porous materials have attracted more and more attention.Porous materials have unique advantages and characteristics,such as high specific surface area,adjustable pore size and chemical composition that can be designed.Today,porous materials have been used in many aspects of our lives,such as electrochemistry,chemical catalysis,adsorption and drug release.With the increasing richness of people's lives and the increasingly serious environmental pollution,the concept of green materials has attracted more and more attention.It is also a trend that traditional porous materials are replaced by new environmentally friendly porous materials.In recent years,purposeful design and synthesis of porous nanoparticles on nanoscale has proved to be a more effective way to prepare multifunctional materials.Porous functional materials with different structures,types,functions and applications can be obtained by reasonable combination of different functional nanoparticles and porous materials.Although there are many porous materials,most of them are based on mesoporous silica,which limits the further application of porous materials.Therefore,further design and construction of more non-mesoporous silica porous materials is particularly important.Only in this way can we further expand the function and practical application of porous materials.Recently,amphiphilic porous solid nanoparticles have attracted more and more attention,because they have amphiphilic properties of surfactants and can be used as oil-water two-phase emulsifiers.Organic solvents are usually used as solvents in organic reactions,but organic solvents are often toxic,polluting the environment and expensive.The use of water instead of organic solvents as solvents has been the goal pursued by many chemists and materials scientists.In the initial studies,surfactants were often added to make water and organic reactants insoluble.However,this method has some shortcomings,because it is difficult to separate and recover the surfactant after the organic reaction is completed,which makes it difficult to further purify the product.Therefore,amphiphilic solid nanoparticles with surfactant properties are continuously prepared.Amphiphilic solid nanoparticles can make the oil water two phase system form Pickering emulsion.After the organic reaction is completed,the amphiphilic solid nanoparticles can be separated by centrifugation.Moreover,the amphiphilic solid nanoparticles after separation can be reused repeatedly to protect the environment and reduce the reaction cost.From the functional point of view of porous materials,the amphiphilicity of porous materials is selected as the research object,and the nanostructure of porous materials is redesigned to prepare new porous materials with amphiphilicity.The applications of the newly designed amphiphilic materials in the formation of Pickering emulsion and catalysis were also studied.In the second chapter,a new idea and method for the synthesis of amphiphilic solid nanoparticles are introduced.We summarized the limitations of these methods by reviewing the current methods of synthesizing amphiphilic solid nanoparticles.At present,there are two main methods to prepare amphiphilic solid nanoparticles,which can be summarized as follows: firstly,to control the synthesis of amphiphilic solid nanoparticles by adjusting the proportion of hydrophilic and hydrophobic parts;secondly,to synthesize solid nanoparticles without amphiphilic properties,and then to modify amphiphilic groups on the surface of solid nanoparticles by "post-grafting" method.For example,quaternary ammonium salt groups.However,there are some shortcomings and limitations in the two methods of preparing amphiphilic solid nanoparticles.We first proposed the concept of amphiphilic organosilicon framework(AOF),and synthesized amphiphilic solid nanoparticles by hydrolysis of amphiphilic organosilicon precursors.The amphiphilic solid nanoparticles synthesized by our new method have good amphiphilic properties,which can make oil water form Pickering emulsion,and the vacuoles with diameters of about 30 to 40 microns can be observed under optical microscope.This is much smaller than the diameter of the emulsion of the amphiphilic solid nanoparticles prepared by the method of "post grafting",which is prepared by preparing the amphiphilic solid nanoparticles prepared by adjusting the proportion of the hydrophilic part to the hydrophobic part and by the "post grafting" method.The diameter of the emulsion vacuole is 80-100 microns.This indicates that the amphiphilic silica skeleton(AOF)nanoparticles prepared by our new method have better amphiphilicity.TS-1 was implanted into the AOF shell as a catalytic center to form a TS-1@AOF Pickering catalyst with yolk-shell structure.In Chapter 3,we used the amphiphilic TS-1@AOF solid nanoparticles as amphiphilic catalysts for emulsification and catalytic experiments.The epoxidation of 1-hexene was chosen as a probe reaction to carry out catalytic experiments.The optimum catalytic conditions of TS-1@AOF solid nanoparticles were explored at different temperatures,catalyst dosage,water to 1-hexene ratio and reaction time.Under the optimum catalytic conditions,the catalytic activity of TS-1@AOF Pickering catalyst was 11.2 times that of TS-1,and the selectivity of 1,2-epoxyhexane was 97.8%.The experimental results show that our TS-1@AOF catalyst has good catalytic activity and selectivity.We believe that the concept of amphiphilic organosilicon framework(AOF)proposed by us provides a new idea for the preparation of amphiphilic solid nanoparticles.Moreover,the amphiphilic AOF nanocatalysts will be unique compared with the traditional amphiphilic solid nanoparticles in the catalytic reaction at the aqueous interface.