Design And Synthesis Of Mesoporous Coated ZIF-8 Yolk Shell Type Catalytic Materials

Over 90% industrial processes have used catalysts,catalysis technology is the generic core technology of the energy industry,and the technology of catalyst is the key of catalytic technology.Owing to their huge specific surface area,abundant pore structure,tailorable construction and modifiable functionality,metal-organic frameworks(MOFs)are regarded as a kind of potential catalysis materials.Much research efforts of MOFs focus on the field of gas storage and gas separation,but the studies of MOFs as a catalytic materials are much less,this is mainly for the reason that MOFs have low hydrothermal and chemical stabilities.Among numerous MOFs,ZIF-8 possesses high hydrothermalstability,huge specific surface areas and flexibleporous channels,which makes it possible to be efficient catalyst carriers where active components,noble metal were loaded.When ZIF-8 is used as catalyst carriers in reactions,the catalytic active centers have weak strength with ZIF-8 and it is easy to run away from ZIF-8's surface.Further more,its low stability in acid or alkali atmosphere limit its application in catalysis.By coating ZIF-8 with inorganic porous materials,the contact between ZIF-8 and acid or alkali can be partly avoided,thus improving the durability of ZIF-8 to acid and alkali.Now there is still no report on coating ZIF-8 with mesoporous materials.The reasons for this result are as follows: ZIF-8 is a kind of hydrophobic material,but the silica shows hydrophilicity,phase separation appears during the coating process,so it's hard to form core-shell or yolk shell structure.In this paper,we successfully synthesized ZIF-8 with a mesoporous silica shell through soft template method by carefully choosinga proper surfactant.In order to study the effect of ZIF-8 and mesoporous silica shell on the catalytic properties of this yolk shell materials,we synthesized Ag/ZIF-8@Ms,ZIF-8,ZIF-8@Ms and Ag/ZnO@Ms.We studied the ph stability of ZIF-8 and ZIF-8@Ms composite.Besides,the catalytic performance of this composite was studied after loading with silver nanoparticles.By comparing the catalytic performance of different materials,we discuss the influence of different structure and components to the catalytic performance.P-nitrophenol was chosen as the target reactant to detect the catalytic effect of the catalyst.The conversion of ZIF-8/Ag@Ms to p-nitrophenol is higher than 95%,and the conversion is over 90% just 15 min after the reaction,which proves the high catalytic performance of our material.