Font Size: a A A

Synthesis,Structure And Catalytic Properties Of Novel Polyniobium Oxygen Clusters

Posted on:2022-05-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:T T ZhangFull Text:PDF
GTID:1481306329967239Subject:Inorganic Chemistry
Abstract/Summary:PDF Full Text Request
Metal-Oxogen Clusters,as an important part of the field of inorganic chemistry research,have always been a popular direction for scientists to explore due to the diversity of their structures and functions.In terms of element composition,metal-oxygen cluster compounds can be divided into four categories:molybdenum oxide clusters,tungsten oxide clusters,vanadium oxide clusters and niobium oxide clusters.Co mpared with the other three metal-oxygen cluster compounds,the research and development of niobium-oxygen clusters have been greatly hindered due to the particularity of the synthesis of niobium-oxygen clusters.Nevertheless,the unique structure and prop erties of niobium-oxygen clusters have attracted the attention of more and more inorganic chemists.In this paper,a variety of synthetic techniques(hydrothermal,normal temperature,and the combination of hydrothermal and normal temperature)were used to synthesize eighteen niobium-oxygen cluster compounds.First,the X-ray single crystal diffraction technique was used to determine and analyze their crystal structure,and then through a series of characterization methods such as:PXRD,ICP,EDS,IR,UV,a nd magnetic analysis to further perform their corresponding characterization s.On the basis of the characterization test,as a catalyst the catalytic performance of the compounds in the styrene oxidation reaction,photocatalytic reaction and electrocatalytic reaction is mainly studied.1.Using hydrothermal synthesis or a combination of hydrothermal and normal temperature synthesis methods,six niobium oxide clusters(Compounds 1-6)with novel structures have been successfully synthesized.Among them,compounds 1-5 are the Keggin-type structure niobium oxide cluster compounds,while compound 6 is a vanadium niobium oxide cluster compound with{V4Nb6}structure,and compounds 1-4 are synthesized for the first time.Compound 1 is a Keggin-type niobium-oxygen cluster compound with Si as the central atom having double Nb caps structure.Compound 2 is the first Keggin-type niobium-oxygen cluster compound with V as the central atom having double V caps and one of the V cap is chelated with an organic ligand.Compound 3 is a rare four-V caps 1D chain niobium-oxygen cluster compound.Compound 4 is a Keggin-type niobium-oxygen cluster dimer with double Sb caps.We studied the performance of ph otocatalytic hydrogen production and epoxidation of styrene on compounds 1 and 2,and analyzed the photocatalytic ability of compound 1 in the photodegradation of Rh B dyes.For compounds 3-6,we have systematically studied the optimal reaction conditions a s styrene epoxidation catalysts and the effects of the contained components on the catalytic reaction.K3[Nb2O2][H7Si Nb12O40]·16H2O(1)[Cu(en)2]9[(VNb12V1.69Nb0.31O42en0.31)2]·20.69H2O(2)K0.25[Cu(en)2]3.5[Cu(en)2(H2O)][VNb12V4O44][OH]2.25·2.25H2O(3)[Cu(en)2]3[Cu(en)2(H2O)]3[Cu(en)2(H2O)2]3{[Cu(en)2][Si Nb12Sb2O40]2}·25H2O(4)[Cu(en)2]2[Cu(en)2(H2O)2]4[Si Nb12V2O42]·7H2O(5)[Cu(en)2]3{[Cu(en)2][H2V4Nb6O30]}·12H2O(6)2.Using normal temperature synthesis or a combination of hydrothermal and normal temperature synthesis methods,five middle-core niobium oxide clusters(Compounds 7-11)with copper-ethylenediamine(Cu-en)as transition metal organic complexes were successfully synthesized.Among them,compound 7 is a like Wells-Dawson structure heteropoly niobium-oxygen cluster with 18 shell atoms and two central heteroatoms.In compound 8,{B-Si Nb6O26}is used as a bridge to connect two complete{Nb6O19}to make it present a crescent-like cluster structure.The epoxidation properties of styrene and the oxygen evolution reaction(OER)catalytic properties of the compounds 7 and 8 were studied.The cluster anions of compounds 9-11 are all{Nb24}bowl-like clusters composed of three Lindqvist type{Nb 6O19}and one{Nb6O30}with a ring structure.Different metal-organic complexes make compounds 9-11 show different structures,and we further studied the catalytic performance of the three compounds as catalysts in the photocatalytic degradation of dyes,styrene epoxidation,and oxygen evolution reaction(OER).Na12[Cu(en)2(H2O)2]5[H3(Si OH)2Si2Nb16O54]2·52H2O(7)K4[Cu(en)2(H2O)2]2[Cu(en)2(H2O)]2[Cu(en)2][Si Nb18O54]·16H2O(8)[Cu(en)2]9.75[Cu(en)2(H2O)]4[KNb24O72H9.25]2·36.5H2O(9)[Cu(en)2][Cu(en)2(H2O)]12[Cu(en)2(H2O)2]3[KNb24O72H7(H2O)2]2·99H2O(10)[K(H2O)4][Cu(en)2(H2O)2]5[Cu(en)2(H2O)]8.25[Cu(en)2]2[K0.5Nb24O72H7.75]2·115.31H2O(11)3.With the hydrothermal synthesis technology successfully synthesized seven Keggin-type Nb/W mixed metal oxygen clusters(Compounds 12-18)with different metal organic complexes.In compound12,its Keggin-type cluster structure is connected with three[Cu(en)2(H2O)]2+transition metal organic complexes to form a three-supported structure.Compound 13 contain s two organic ligands and glycolic acid is obtained by in-situ one-step oxidation of acetic acid molecules.Compound 14 also contains two transition m etal organic complexes,and the oxalic acid ligand is obtained by two-step in-situ oxidation of the acetic acid molecule.Compound 15 only contains one N-containing organic ligand-phen,and there is a?···?interaction between the adjacent Cu-phen fragments.For compounds 16 we successfully introduced aromatic acids as organic ligands into Nb/W mixed metal oxygen clusters for the first time.In compound 17,the niacin molecule used as the raw material undergoes in-situ oxidation to generate hydroxynicotinic acid and participates in the synthesis of compound 17 as an organic ligand.Compound 18 is the only one in which Zn element is introduced as a transition metal in the series of Nb/W mixed metal oxygen clusters of compounds 12-18,and a crab-like cluster structure is formed under the joint action of the cluster anion and the transition metal organic complex.Part of the testing of the properties of the series of compounds is still in progress.Here we mainly reported the catalytic performance in electrocatalysis and styrene oxidation reaction with the compounds 13 and 14 as the catalysts.[Cu(en)]0.75{[Cu(en)2(H2O)]3[H0.625Si W9Nb3O40]}2·14.5H2O(12)[Cu(2,2'-bpy)(H2O)]4[Cu(2,2'-bpy)(glc)]2{[Cu(2,2'-bpy)][HSi W9Nb3O40]}2·4H2O(13)[Cu4(2,2'-bpy)4(OH)4(H2O)2]{[Cu2(2,2'-bpy)2(ox)][HSi W9Nb3O40]}·3H2O(14){[Cu(phen)(OH)][Cu(phen)(H2O)]}4[H2Si W9Nb3O40]2·16H2O(15)[Cu(phen)(H2O)2]2{[Cu(phen)(H2O)]2(nic)}[Si W9Nb3O40]·7H2O(16)K[Cu(phen)(H2O)]6[Cu(phen)(hnic)]2[H0.5Si W9Nb3O40]2·14H2O(17)K2[Zn2(phen)(OH)]4[Si W9Nb3O40]2·7H2O(18)...
Keywords/Search Tags:Niobium-oxygen clusters, Organic-inorganic hybrid materials, Crystal structure, Characterization, Styrene oxidation, Photocatalysis, Electrocatalysis
PDF Full Text Request
Related items