Synthesis And Catalytic Performance Of Hierarchical Composited Materials: The Encapsulation Of Polyoxometalate In Metal-Organic Frameworks

Polyoxometalates?POMs?,as a metal-oxo cluster compound,possess both acidity and redox,and are known for pseudo-liquid phase behavior,structure diversity and multi-functionality.Although POMs homogeneous catalysts have showed high activity and selectivity,mild operating conditions,etc.,but they also show obviously deactivation and recycle difficulty,small specific surface area of solid POMs(<10 m²·g^-1)and lacking of surface active sites,all of these limited its catalytic properties.New porous metal-organic frameworks?MOFs?material are an ideal carrier for preparing POMs heterogeneous catalysts,because of its stable crystalline porous structure,large specific surface area,tunable pore size rules and modified pore surface.Herein,we focus on the syntheses of supported catalysts which have a large surface area,easily to be separated and recycled.Then,the supported catalysts were used for the photocatalytic degradation of dye waste water and oxidative-extraction desulfurization of model diesel.In this paper,a novel hierarchical meso-/microporous material POMs@HKUST-1 has been obtained through hydrothermal synthesis for the first time.In this assemble process,we use HKUST-1 as confined host,Keggin type POMs as encapsulated guest and CTAB as structure-directing agent,respectively.The other two hierarchical materials,POMs@MIL-101and POMs@Uio-67 have also been achieved successfully through?bottle around ship?method.The physical characterization has confirmed that POMs are encapsuled and dispersed in three MOFs at molecule level.Furthermore,the synthesis condition,assemble method and regularity are investigated.The advantages of three MOFs as new supporter for POMs have been discussed.The composition,structure and morphology of materials have been analyzed through different characterization methods.Furthermore,the catalytic performance of title composited materials was investigated in oxidative system.POMs@HK UST-1 and POMs@MIL-101 showed excellent catalytic activity in photocatalytic degradation of methylene blue,POMs@MIL-101 and POMs@Uio-67 showed excellent catalytic performance in the oxidation removal of dibenzothiophene.The results shows that,under the optimal conditions,the degradation rates of POMs@HKUST-1 and POMs@MIL-101can reach up to 92%and 96%,respectively.Moreover,POMs@MIL-101 and POMs@Uio-67 also showed excellent catalytic performance in oxidative desulfurization?ODS?of DBT,the best ODS rate of POMs@MIL-101 can reach up to 100%.Through analysis,characterization and crystal structure,we explored the correlationship between the chemica l composition,structure and the properties of bi-functional catalyst POMs@MIL-101,and obtained the assembling strategies,and expound the mechanism of catalytic oxidation coupled with selective adsorption,and reveal the confinement effects of host,as well as?absorption-degradation?oxidation??synergistic effects of host-guest.The results of above-mentioned research will supply experimental data and evidence for the application of POMs@MOFs composite in the reaction process.