| With the development of social industrialization,problems such as energy shortage and environmental pollution have become increasingly prominent,and people's awareness of environmental protection is also increasing.Therefore,since the notion of "Green Chemistry" was proposed,more and more researchers have devoted their research interest to the field of green chemistry.However,at present,most organic chemical reactions inevitably use toxic,highly polluting and expensive organic solvents as reaction media.With the advantages of no pollution,low cost and easy availability,water has been gradually used as the medium of many experiments.Nevertheless,it is not easy for water and most organic substrates to dissolve each other,resulting in the reduction of reaction interface area and reaction efficiency.In order to solve this problem,people emulsify the immiscible two phases by adding molecular surfactants to the oil-water two phases,so as to improve the efficiency of aqueous organic reaction.These added surfactant molecules will be mixed with the target outcome,causing it very difficult to purify the product.The amphiphilic porous nanoreactor loaded with catalytic active center can not only dissolve oil and water through emulsification and improve the reaction efficiency,but also easily separate and recover it from the final product by centrifugation or filtration after the organic reaction.The recovered amphiphilic porous nano reactor can be reused for many times,which greatly saves the cost of chemical reaction and protects the environment.Therefore,it is very important to design and construct amphiphilic porous nano reactor with adjustable hydrophilicity/ hydrophobicity for green catalysis.Starting from the concept of "green chemistry",this paper has successively designed and constructed two kinds of amphiphilic porous nano reactors of noble metal nano particle type and non-metallic ion type,which can be used for efficient catalysis of organic reactions with water as solvent.It is worth noting that we did not simply aim at the synthesis of amphiphilic porous nanoreactors,but realized the conceptual transformation from "the design and synthesis of nanoreactors with precious metal nanoparticles as catalytic active centers" to "the design and synthesis of nanoreactors with non-metallic ions as catalytic active centers".This is because we realize that nonmetallic catalysis has broader application prospects than "delicate" noble metal catalysis.Because the application of sensitive precious metals is too complex and expensive,it is not disagreed with "Green Chemistry".Interestingly,American scientist David W.C.Mac Millan also gave up the "delicate" metal catalyst and won the 2021 Nobel Prize in Chemistry for developing "asymmetric organic catalysis".It can be seen that "non-metallic catalysts have unlimited application space" has become the consensus of international scientists,which also coincides with our concept.On the other hand,amphiphilic porous nano reactor is basically widely used in oil-water twophase reaction system,that is,the organic reaction in which water is used instead of organic solvent as the reaction medium.However,there are few reports that amphiphilic porous nano reactors have been applied to other types of organic reaction systems.In this thesis,we also discuss a special kind of reaction,that is,the reversible reaction produced by the reactant itself as the reaction solvent and water as the by-product.For the sake of making this kind of reversible reaction move to the positive direction as much as possible,people often need to add water carrying agent to the system.The use of water carrying agents such as toluene and cyclohexane will also cause environmental pollution and increase the reaction cost.Here,we will try to apply the newly constructed non-metallic ion amphiphilic porous nano reactor to the above system,which can efficiently catalyze this kind of reversible reaction without adding water carrying agent.This not only protects the environment and saves the cost of chemical reaction,but also expands the application scope of amphiphilic nanoreactor.At the same time,it also provides an innovative way for amphiphilic nanoreactor.Therefore,the research content of this paper is closely around the concept of "green chemistry",and there is a deep relationship between the research contents.In Chapter 2,palladium nanoparticles with catalytic active centers were successfully implanted into vinyl pyridine doped mesoporous silicone with hollow structure by growth induced corrosion method.We obtained a yolk-shell "smart" amphiphilic porous nanoreactor with two catalytic active centers.The two active centers are weakly basic pyridines in the framework and palladium nanoparticles in cavities.Interestingly,we found that the obtained vinyl-pyridyl doped nanoreactor can more easily adsorb hydrophobic molecules containing nitro or vinyl into it,rather than simply adsorbing all substrates indiscriminately.When it is used as a catalyst for Knoevenagel-hydrogenation reaction,the reactants containing nitro groups are easily adsorbed into the channels,and then Knoevenagel reaction occurs under the catalysis of weakly basic pyridine groups on the surface of mesoporous pores to form intermediates containing vinyl groups,and the intermediate containing both nitro and vinyl is more likely to continue to be adsorbed by the vinyl-pyridyl doped pores,which speeds up the rapid transmission of reactants and intermediates.Therefore,without the addition of other bases,our new nanoreactor can efficiently catalyze the smooth progress of the above reactions,protect the environment and save the cost of chemical reaction.Most importantly,only in hydrogen atmosphere,this amphiphilic nanoreactor with "space separation catalytic active center" can catalyze the above series reaction by one pot method.This is very important because most of the so-called tandem Knoevenagel-hydrogenation reactions reported in the past are actually carried out in two steps,that is,Knoevenagel reaction in air environment and hydrogenation reaction in hydrogen environment.Therefore,when using our "smart" amphiphilic porous nanoreactor to catalyze the Knoevenagel-hydrogenation reaction,it can simplify the cumbersome operation and save a lot of manpower,which is also in line with the concept of "green chemistry".In Chapter 3,a novel mesoporous Salt of Organosilicon Framework(SOF)nanoreactor was designed and constructed.We first designed and synthesized an organosilane 2,5-bis [(E)-2-(triethoxy silicon)vinyl] pyridine precursor,and then synthesized the porous organosilicon skeleton with a large number of pyridine groups in the framework by sol-gel method.Finally,the porous skeleton was protonated with hydrogen bromide solution to obtain a novel silicone skeleton salt nanoreactor.This is an ionic nanoreactor whose catalytic active center is located in the pore.It can not only be used to emulsify a variety of oil-water biphase systems,but also catalyze the conversion of olefins to dibromoalkanes in aqueous medium.In previous reports,organic solvents are used as reaction media in the dibromination of olefins,which will produce a large number of by-products when reacting in water.When our SOF nanoreactor is used to catalyze the reaction,it can efficiently catalyze the dibromination of olefins with water as the reaction medium.The catalyst still has good stability and catalytic performance after 8 cycles.Therefore,the design and construction of the novel mesoporous SOF nanoreactor not only avoids using the organic medium,protects the environment and reduces the cost of chemical reaction,but also further deepens people's further understanding of green olefin addition reaction.In Chapter 4,another amphiphilic Salt of Organosilicon Framework(SOF-II)nanoreactor was designed and constructed.The nanoreactor can be ionized into a silicone skeleton with a large number of cations embedded on the surface and anions free around the cations(due to electrostatic gravitational interaction).The silicone skeleton nanoparticles embedded with a large number of cations on the surface have amphiphilic,that is,they have the ability to emulsify a variety of oil-water biphasic systems.Similar to molecular Surfactant CTAB,its hydrophilicity comes from the embedding of a large number of cations on the surface,while its lipophilicity comes from a large number of organic groups in the skeleton.In addition,the free anions in the mesoporous channels due to electrostatic gravitational interaction can be used as the active center of Ketone-alcohol condensation reaction,and it has satisfactory catalytic performance.The amphiphilic porous nanoreactor has been applied to this kind of reversible reaction with reactant itself as solvent and water formation in the product.In previous reports,in order to make the above reversible reaction move to the positive reaction direction as much as possible,toxic water-carrying agents such as toluene and cyclohexane are often used.The use of water carrying agents will also cause environmental pollution and increase the cost of chemical reaction.When using our new amphiphilic nanoreactor as catalyst,because its amphiphilic framework has stronger lipophilicity than hydrophilicity,it is more conducive to the preferential desorption of water molecules from the pores of the nanoreactor,so as to separate water molecules from the catalytic center in space.Therefore,the novel amphiphilic porous SOF-II nanoreactor can still efficiently catalyze the reversible Ketone-alcohol condensation reaction without using toxic water-carrying agents.This protects the environment and saves the cost of chemical reaction.At the same time,it also provides a new idea for people to further understand the potential application of amphiphilic nanoreactor. |
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