The Synthesis And Catalytic Properties Of Porous Magnetic Composite Materials

The hierarchically porous materials possessing well defined macropores and interconnected meso-and micropores and its potential technological impact in adsorption,separation,catalysis,energy storage and environment have attracted much attention.A facile synthetic approach for preparing magnetic porous catalysts including hierarchically porous silica materials by the sol-gel method and hollow magnetic porous Zirconia fibers based on electrospinning is reported here.After surface functionalization,hierarchically porous materials have new chemical properties through the adjustment of surface properties,the main research results are as follows:(1)A facile synthetic approach for preparing porous magnetic catalysts,on which various inorganic compounds are alternately loaded using a pyrogallic acid(PG)-assisted layer-by-layer(LbL)coating was reported here.The PG forms an adhesion and reductive layer on the surface of hierarchically porous silica,and Pd,Al2O3,ZrO2,or FeOx can then be introduced on the surface of the material.Compared with the conventional impregnation method,the PG layer obviously improves the dispersion of catalysts and greatly reduces the blocking of the pores.At the same time,the reduction properties of the layer help to reduce the diameter of the Pd nanoparticles to 5±1.3 nm.The Fe3+ ions are partially reduced into Fe2+ by the PG layer to form Fe3O4,which endows the porous catalysts with a magnetic separation property.The synthesized multicomponent catalysts show excellent catalytic activity for various reactions,including the Suzuki Miyaura coupling,reduction,Knoevenagel condensation and Friedel–Crafts alkylation reactions.The TOF values show an improvement of 2 to 4 times over those of the catalysts prepared by the traditional impregnation method.The multicomponent porous magnetic catalysts also exhibit superior catalytic performance for many one-pot multistep cascade reactions.(2)A facile synthetic method for preparing hollow magnetic porous Zirconia fibers based on electrospinning and its application as a solid acid catalyst for dehydration of D-fructose into 5-HMF is reported here.First,we prepared the uniform hollow porous ZrO2 nanofibers by employing the coaxial electrospinning technique followed by subsequent heat treatment.Using a specially designed electrospinning solution,by adding magnetic particles to the electrospinning precursor solution,we can conveniently assemble magnetic nanoparticles into the internal surface of the hollow fibers.The hollow magnetic porous zirconia fibers have a BET specific surface area of 34.70 m2 g-1,secondary pore structure at 19 nm and 3.9 nm and a pore volume of 0.18 cm3 g-1.At the same time,they have high acid sites loading upon sulfation and good hydrothermal stability.The sulfonic fibers exhibit extremely excellent catalytic performance when considering the formation of 5-HMF from D-fructose.More importantly,the electrospun porous magnetic fibers have unique magnetic properties and can be easily removed and reused,showing great potential for practical applications.