Preparation And Catalytic Performance Of Core-Shell Nanocomposites

Compared with traditional materials,nanocomposites which have special structure and morphology tend to show better performance in the field of catalysis.Core-shell nanocomposites can not only make various kinds of materials cooperate with each other,but also make up disadvantages of single material,because they combine the advantages of shell and core.The core can provide multiple and dispersed active loading points,and the shell can prevent the agglomeration of the core and protect the active sites.If there is a cavity in the core-shell structure,the reaction solution can be collected and accelerate the reaction.In this paper,one kind of core-shell structure without cavity and two kinds of core-shell structure with cavity are fabricated by using different shell and core materials respectively.The properties of the materials are investigated by catalytic reaction and the advantages and application prospects of core-shell materials are studied.1.The MOF of ZIF-67 and Zn-BTC are prepared by self-assembly method,and then the Zn-BTC@ZIF-67 aggregates are synthesized by dispersing them in solvent according to a certain mass ratio.Finally,CNF@CoOx-N-C core-shell nanocomposites are obtained by aggregates transformation at high temperature.The materials' properties are characterized by UV-vis,XPS,and etc.CNF@CoOx-N-C are used as catalysts for reduction of p-nitrophenol.The results show that the core-shell CNF@CoOx-N-C has the best catalytic activity.It has a specific rate constant of 6.88 s-1·g-1 for reduction of p-nitrophenol.Furthermore,the magnetic core makes the materials easy to recycle.2.The core-shell Fe3O4-NH-Ru@void@PMO composite materials which are modified with hexanediamine and loaded with metal Ru as core and PMO as shell are synthesized through a combination of coating and in-situ growth etching method.The materials' properties are characterized by ICP-AES,FT-IR,and etc.Which are used as catalysts for levulinic acid to ?-valerolactone.The results show that the hexanediamine can not only protect the spherical structure of Fe3O4 from destruction,but also fix the Ru on the core.The conversion rate of target product is close to 99%.The yield is 98%,and the magnetic core makes the materials easy to recycle.3.Metal-acid bifunctional Ru@C-SO3H materials are synthesized:First,SiO2 microspheres are synthesized by Stober method,and chitosan modified with 8-hydroxyquinoline are introduced to form coated structure.after solid-state transformation at high temperature,HF etching and sulfonation of chlorosulfonic acid,materials are impregnated with ruthenium trichloride solution and reduced by H2.The materials are studied by the reaction of cellulose to isosorbide.The results showed that when the carbon source delay time is 12 h,the yield of the target product is the highest,in which the conversion is 100%and the yield of isosorbide is 39.5%.