Construction And Applications Of Noble Metal-Loading Organic-Inorganic Nanohybrid Materials Based On Mussel-Inspired Chemistry

Noble metal nanoparticles?NPs?have broad application potential in catalysis,electrochemistry,optics,chemical sensors and biological detection owing to their advantages of small size,large specific surface area,and good stability.However,the serious aggregation and instability of nanoparticles would hinder their catalytic efficiency.Therefore,how to prevent their aggregation is crucial to the catalytic effect of metal nanoparticles.In recent years,a lot of researches have been carried out to load metal nanoparticles on different organic and inorganic solid supports.On the one hand,which can help improve the stability and dispersibility of metal nanoparticles.on the other hand,the synergistic effect among the components of metal nanocomposite catalysts can significantly improve the catalytic reaction activity and selectivity.In addition,polymer modification can also improve the surface characteristics and dispersibility of the catalyst supports,and further enhance the catalytic performance and recycling stability of catalysts.In this thesis,the controllable synthesis of catechol-formaldehyde resin?CFR?microspheres was successfully carried out,and different structures of nanohybrids was constructed based on the mussel chemical function of catechol by combining the CFR microspheres and polymers with magnetic nanomaterials,carbon dots?CDs?and two-dimensional?2D?layered double hydroxide?LDH?materials.A series of new nanohybrid catalysts were prepared by loading precious metals on these nanohybrid supports.The applications of these designed nanocatalysts in organic catalytic reactions were mainly studied.The specific research contents are as follows:?1?Catechol and formaldehyde resin?CFR?microspheres were successfully prepared by solvothermal method using catechol and formaldehyde as raw materials under alkaline conditions.We systematically studied the effects of different reaction parameters such as the ratio of catechol to formaldehyde,the ratio of ethanol to water,ammonia concentration,and temperature on the size and morphology of the synthesized CFR microspheres,and finally obtained the optimal reaction conditions.The results showed that the size of CFR microspheres can be controlled between50-800 nm via changing experimental conditions.And under different conditions,the morphology of CFR microspheres is significantly different.In addition,CFR stabilized Ag nanoparticle hybrid materials?CFR@Ag?were constructed by in situ reduction route using the reduction and strong coordination ability of catechol groups on the surface of CFR microspheres as a support.It was also found that CFR microspheres treated with alkali solution could load silver nanoparticles on their surface or inside.The prepared CFR@Ag and TCFR@Ag nanocomposites can not only be used as efficient nanocatalysts for reducing dyes and 4-nitrophenol with good cycle stability,but also as excellent antibacterial agents to inhibit the growth of E.coli and S.aureus for a long time up to 68 h.?2?Fe₃O₄@CFR core-shell magnetic nanospheres were prepared by hydrothermal method,and the thiol terminated poly?N-isopropylacrylamide??PNIPAM?thermal responsive polymer brushes were successfully grafted onto the surface of the CFR shell of Fe₃O₄@CFR to obtain Fe₃O₄@CFR-S-PNIPAM hybrid materials through mussel-inspired chemistry.Then,Fe₃O₄@CFR-S-PNIPAM@Pd/CDs nanohybrid catalyst material with uniformly loaded palladium nanoparticles was constructed by in-situ reduction using the synthesized aminopyridine derived coordination functional carbon dots?CDs?as reductant and stabilizer and Fe₃O₄@CFR-S-PNIPAM as a support.We systematically studied the effects of the molecular weight and grafting density of the PNIPAM brushes and CDs content on the microstructure and catalytic activity of the as-prepared nanohybrid catalysts.Due to the special role of polymer brushes on the nanocatalysts and the electronic synergistic effect between Pd NPs and CDs,it was found that the obtained nanocatalyst displayed high catalytic reduction performance for organic dyes(TOF value of MB:962.9 min^-1)and p-nitrophenol(TOF value:128.6 min^-1),and the catalytic efficiency is better when the PNIPAM chain is longer.At the same time,the designed magnetic nanohybrid catalysts also revealed excellent catalytic efficiency for Knoevenagel condensation and Suzuki cross-coupling reaction.Additionally,PNIPAM functionalized nanocatalysts also exhibited interesting temperature response behavior in the catalytic reduction process.?3?Polymer modified two-dimensional layer double hydroxide?LDH?nanosheet stabilized palladium hybrid catalysts were constructed by mussel-inspired chemistry method.Firstly,MgAl-LDH two-dimensional lamellar material was synthesized by hydrothermal method.Then,under alkaline conditions,the polydopamine was deposited on the surface of LDH by mussel-inspired chemistry,and the sulfhydryl-capped PNIPAM was grafted onto the LDH@PDA hybrid material by Michael addition reaction.Finally,CDs were used as reductant and stabilizer to prepare LDH@PDA@PNIPAM@Pd/CDs hybrid nanocatalyst by in situ loading metal Pd onto PNIPAM modified LDH@PDA.In addition,the LDH@PDA@PNIPAM@Pd control catalyst was also synthesized by using NaBH₄ as reducing agent.Compared with LDH@PDA@PNIPAM@Pd catalyst without CDs modification,the designed nanohybrid catalyst LDH@PDA@PNIPAM@Pd/CDs with temperature-responsive catalytic behavior have better catalytic reduction ability for various dyes and nitrophenol due to its highly dispersion stability and synergistic catalytic effect between metal active center and CDs.In addition,the prepared nanocatalyst also has excellent catalytic performance for the Knoevenagel condensation reaction.