Polyoxometalates-assisted Synthesis Of Noble Metal Nano-materialsand The Study Of Its Catalytic Property

Noble metal nanoscopic materials have aroused great research interest owing to their unique properties and potential applications in biological and chemical sensing,optoelectronics and catalysis.The synthesis of noble metal nanomaterials with small size,controllable morphology,uniform size distribution,stable structure and easy recovery in mild conditions have been a focus in the research.Based on previously synthetic strategies for POM-noble metal nanomaterials,a new approach has been developed.And the catalytic performances of the materials have been investigated.The aim of the research is to develop a facile and green method to prepare noble metalutilizing the unique properties of POMs as both reducing and capping agents.We also explored the catalytic activities of the as-prepared composites and tried to expound the possible catalytic mechanisms in the catalytic reactions.1.We construct a Surfactant-Encapsulating Polyoxometalate?SEP?nanowire assembly prepared from hexadecyltrimethyl ammonium bromide?CTAB?and POM(H3PW₁₂O₄₀)in the n-butanol/acetone mixed reaction system.The SEP nanowire was as new carrier for noble metal nanoparticles.After irradiation of SEP nanowire assemblies with UV light,the POM units in the SEP assemblies have been reduced to heteropolyblue?HPB?species.The Ag+ ions on the surface of nanowires were in situ reduced into Ag NPs,forming new composite catalyst Ag/CTAB-PW₁₂?1?.The loading amount of Ag NPs on the SEP nanowire assembly can also be tuned by the addition of different concentrations of AgNO3 solutions,the diameter of Ag NPs on the SEP nanowire assembly is in the range of 10±2 nm.Such Ag/CTAB-PWi2 composite catalyst exhibits good catalytic activity and stability in the reduction of 4-nitrophenol?4-NP?with NaBH4 in isopropanol/H2O solution.The rate constant k was calculated to be 3.15X10-3 s-1 for Ag5.39/CTAB-PW₁₂ composite material.After three cycles of the catalytic reduction experiments,no significant loss of catalytic performance.2.Through the solid-phase reaction route,the Ag+ as the counter cationto formed insoluble POM-based salt.After UV irradiation,the poly anions act as both reducing and capping agentsto reduce Ag+,forming a series of composite materials Ag/AgnPOMs.They exhibit enhanced visible light-driven photocatalytic performances for degradation of Cr?VI?and methyl orange?MO?.The loading amount and morphology?geometric shape and dimension?of Ag NPson the photocatalysts can be tuned by the POManionscharges over a range.Ag_x/Ag_3-x[PW₁₂O₄O]?2?Ag_x/Ag_4-x[SiW₁₂O₄O]?3?Ag_x/Ag_5-x[BW₁₂O₄O]?4?Ag_x/Ag_10-x[P₂W₁₇O₆₁]?5?Ag_x/Ag12-x[P₂W₁₅O₅₆]?6?3.We have carried out the design and synthesis of POM-based metal organic complex with new components and structure:[Cu?bppdo??Hbppdo??MeCN?3][PW₁₂O₄O]CH₃CN?7?[Co?2,2'-bpdo?₃]₂[PWi₂O₄O]CH₃CNH₂O?8??L1 = 2,2'-bipyridine-N,N'-dioxide,L2 = 1,3-bis?4-pyridyl?propane-N,N'-dioxide?Cyclic voltammograms suggested that polyanions were dispersed and enwrapped by the metal organic networks,but the electrochemical behavior of POMs showed negligible change.In addition,these compounds can be found reduced under UV irradiation.The compounds can be found in the reduction under UV irradiation,it is a kind of potential carrierin situ reduced and loading the noble metal nanoparticles.