Microfluidic Synthesis And Catalytic Oxidation Performance Of UiO-66 Metal-Organic Frameworks Modified With Different Functional Groups

UiO-66 is a typical Zr?IV?based MOFs material with good thermal and acid stability.The framework structure remains stable up to 300°C.UiO-66 have broad application prospects in many fields for their uniform pore structure and large surface area.In addition,different functional groups can be introduced on the ligand to modify the MOFs and functionalize the UiO-66 material.At present,UiO-66 mainly synthesized by solvothermal method with batch reactor,the main drawbacks are the long reaction time,and has batch difference,the particle size of synthesized UiO-66 is usually in micrometer scale.Therefore,it is important to develop a continuous and efficient method to prepare UiO-66 materials in nano range.Microfluidic synthesis is an alternative choice.It has the advantages in efficient mixing and heat transfer,thus lead to enhanced reaction rates.Besides,it can realize continuous synthesis and controllable particle size.In this work,a Zirconium based MOFs UiO-66 was synthesized continuously by microfluidic method.The synthesized MOFs samples were characterized by XRD,FT-IR,N₂physical adsorption and SEM.Compared to batch reactor,UiO-66 synthesized by microreactor has a smaller particle size and a narrower particle size distribution.Experiment result shown that Microfluidic synthesis can obtain uniform hexahedral crystalline products in nanometer range?less than 100 nm?.The influences of temperature,total flowrate and residence time on the obtained products were investigated.Higher temperature benefited the growth of crystal.When total flowrate increased,Crystal sizes of UiO-66 synthesized by microfluidic method decreased.Crystal growth required sufficient residence time,but if the residence time was prolonged continuously,the crystal particle size would not change.By optimizing the synthetic parameters,UiO-66modified with different functional groups?namely UiO-66-X?X=NH₂,NO₂,Br??could be synthesized continuously by microfluidic synthesis.For synthesized UiO-66-NH₂ by microfluidic method,The Schiff base group was constructed by post-modification method,and then the molybdenum peroxide was anchored on the MOFs framework via cooridination bond.By this way,MoO?O₂?₂@UiO-66-NH₂ catalyst was prepared and the catalytic oxidation performance of dibenzothiophene?DBT?was explored.The effects of reaction temperature,oxidant type and oxidant dosage on the catalytic oxidation performance of the catalyst were investigated.Blank control experiments and repetitive experiments were also carried out.Studies have shown that increasing the reaction temperature and the amount of oxidant can significantly accelerate reaction rate;at the same temperature,the catalytic oxidation performance order under different oxidants is:CHP>TBHP>H₂O₂.When T=80°C,using CHP as oxidant,O/S=4,the conversion of DBT can reach over 95%after 60 min,and DBT has completely converted after 360 min.The catalyst has stable activity.After four cycles,the conversion of DBT remained above 93%.