New Supported Catalysts Based On Mesoporous MIL101: Preparation And Catalytic Performance

Metal-organic frameworks (MOFs) existe ordered pore structure, high porosity,large specific surface area as well as tunable structure and properties. Due to theseoutstanding properties, MOFs could be used highly desirable and promising catalystsor carrieres for applications in heterogeneous catalysis. In this thesis, MIL MOFs withgood stability, high specific surface area and large pore size have been used to preparea variety of supported catalysts. Their catalytic activity and mechanism were studiedsystematically.MIL-101(Al)-NH2with amino functional groups was chosed as a carrier tosupport active substance Hemin which is the active center of the peroxidase.Hemin@MOF(H@M) composite material has been prepared by dipping method(IMP).The structure was characterized by XRD, SEM, FT-IR, EDS, N2adsorption. Itscatalytic activity was measured and good peroxidase activity was shown by H@M.The catalytic mechanism was studied systematically. A simple, economical, highselectivity, high sensitivity colorimetry method of detecting glucose in water has beenestablished based on the peroxidase-like catalytic activity.Highly dispersed Au, Ag, Pd and AuPd bimetallic alloy with different molarratios catalysts were prepared using a double solvents method. The specific surfacearea, particle size, and metal loading amout of catalysts were characterized by XRD,N2adsorption, TEM, XPS and ICP-AES. The catalytic performance of all theMNPs/MIL-101(Cr) catalysts were determined by the reduction of4-NP to4-APusing NaBH4as reducing agent. The results showed that the particle size of Au NPs,Ag NPs, Pd NPs, AuPd NPs were2.9±0.7nm,1.9±0.6nm,2.1±0.6nm and2.8±0.7nm, respectively. The particle sizes of Pd NPs and AuPd NPs prepared byconventional impregnation method is about8.0nm. Th reaction rate order of Ag NPs,Pd NPs, Au NPs catalysts was Pd NPs> Ag NPs> Au NPs. The activity of Pd andAuPd prepared by DSM is9.6times and8.3times higher than that of Pd and AuPdcatalysts prepared by conventional impregnation method. The structure and activity ofthe catalysts prepared by double solvent method have no significant changes afterthree cycles. In the absence of surfactant stabilizer, core-shell bimetallic catalystAu@Ag/MIL-101(Cr) with AuAg particle size6.3±1.8nm has been prepared bystep deposition reduction method by using the pore confinement effect of carrier. Thecatalyst has exhibited good catalytic activity in4-NP reduction reaction.The activityof AuAg bimetallic core-shell catalyst is5.2times and2.1times higher than that of2Au/MIL-101(Cr) and2Ag/MIL-101(Cr), respectively. Synergistic catalytic effecthas been discovered between Au NPs and Ag NPs.Apparent reaction rate constants kappunder different conditions have beenobtained by studying the catalytic activity under different catalyst concentration,substrate concentration, and temperatures. Intrinsic reaction rate constants k, substrateadsorption constant K4-NPand KBH4, substrate adsorption enthalpy and entropyparameters and the true activation energy EA,k, have been obtained by fitting thekinetics data using the Langmuir-Hinshelwood reaction model. When the substrateconcentration was1mM4-NP and10mM NaBH4, the apparent activation energy ofthe reaction EAwas75.5kJ/mol, pre-exponential factor kapp,0was4.8×1010s-1and theentropy ch nge ΔS was204.5J/(mol K). The study also showed that the inductiontime t0is directly related to the the reaction rate constant k of the controlling step.Theinduction time is also in line with the Arrhenius equation. The rection process can bemonitored by monitoring the changes of induction time.