| In the modern chemical industrial production,nanocatalysis and smart catalysis are the current important trend in the catalytic field.Nanocatalysts have the advantages of small particle size,large surface area,high surface activity,and strong adsorption capacity.These characteristics make nanocatalysts not only greatly improve the reaction efficiency,but also can catalyze chemical reactions that could not be performed.Smart catalyst can achieve the “on/off” state of the catalyst through changed in the external environment,such as light,pH,temperature,electric field,magnetic field,etc.,thereby controlling the reaction process.Therefore,the design and synthesis of smart nanocatalytic systems has become a research hotspot for researchers.In this paper,mesoporous silica nanoparticles(MSNP)was used as a catalyst carrier.With its regular nano-channel structure,the metal nanocatalyst was synthesized in situ and loaded onto a carrier.The preparation process was simple and the effect was favourable.Further,in order to realize the intelligent control of the nanoreactor,a hydrophobic group was grafted onto the surface of the mesoporous silicon nanoreactor,and the temperature-sensitivity effect of supramolecular complexes containing cyclodextrin cavity and hydrophobic group was used to achieve thermal response "on/off" control of the catalytic reaction for the nanoreactor.The first part was the preparation of a nanoreactor containing a dodecyl hydrophobic group.Firstly,we prepared MCM-41 mesoporous silica material by sol-gel method,and then loaded silver nanoparticles in mesoporous silicon channels,and grafted hydrophobic groups(dodecyl chain)on the surface of mesoporous silicon nanoreactorsfor modification,and hydrophobic group-modified nanoreactor material Ag@MSNP-Dod was successfully prepared.And a variety of test methods were used to analyze and characterize it.In the second part,α-cyclodextrin monomer crosslinked with epichlorohydrin to prepare water-soluble α-cyclodextrin polymers(CDP).Nuclear magnetic resonance spectroscopy(NMR),fourier transform infrared spectroscopy(FT-IR),X-raydiffraction(XRD)and thermal analysis(TGA)were used to study and analyze the cross-linked structure and thermal stability of CDP.In addition,the intrinsic viscosity of CDP was also studied and analyzed.Cyclodextrin polymers were primarily intended to form a temperature-responsive composite system in the next step.The third part was to compose water-soluble cyclodextrin polymer(CDP)and mesoporous silica-based materials with hydrophobic groups to form the supramolecular structure system Ag@MSNP-Dod/CDP.The particle size of Ag@MSNP-Dod/CDP at different temperatures was measured using a particle size analyzer to explore the "inclusion/dissociation" effect of the mesoporous silica with a dodecyl chain and the α-cyclodextrin polymer.An UV-visible spectrophotometer was used to characterize the catalytically controllable performance of smart nanoreactors.The study showed that when the system was at 20℃,the dodecyl chain on the nanoreactor is encapsulated into the CDP to form a composite structure,so that the nanoreactor aggregated and precipitated,the average particle size of the system became large;the MSNP channel was Cyclodextrin molecules cover,the reactants could not enter the channel and can not contact Ag nanoparticles,the catalytic efficiency was low.When the temperature of the system raise to a critical value,the Dod group was decomposed with CDP and the particle size of the system decreases;the nanoreactor was in an unaggregated state,and the reactants could smoothly enter the pore and the catalytic efficiency was improved.And this nanoreactor could realize the responsive operation of its catalytic switch through the control of the outside temperature,and showed the reversible catalytic action.This kind of temperature-responsive composite nanoreactor provided new ideas and new methods for the field of controllable catalysis,and had great applications in the purification and separation of catalysts. |
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