| As one of the most researched POMs species,Keggin-type anions own 36 oxygen atoms with coordinating ability and Td symmetry,that guarantee agile stereoscopic orientations and abundant covalent coordination.It is more likely to combine with dissimilar transition metals and organic ligand to form a number of novel structures compounds which have a wide range of applications in the fields of chemistry,materials and medicine etc.Due to the more negative surface charge density of the{BW12}unit,the metal ions are more favourable to forming hybrid multifunctional materials.Therefore,the article has synthesized six organic-inorganic hybrid compounds by hydrothermal method based on{BW12}Keggin structure polyoxometalates and characterized by elemental analysis,IR,TG,SEM and X-ray single crystal diffraction.The molecular formula of the six compounds:[{Ag?phen?2}4{Ag?phen?}2(BW12O40)]?OH??phen=1,10-phenanthroline??1?[{Ag5?pz?7}(BW12O40)]?pz=pyrazine??2?[{Cu?bim?2}][{Cu?bim?2?H2O?}2][{Cu?bim?2}2(BW12O40)2]·6H2O?bim=biimidazole??3?[{Cu?bipy?2}][{Cu?bipy?2}2(BW12O40)]?OH??bipy=2,2?-bipyridine??4?[{Cu?en?2?H2O?}][{Cu?Hpdc??en?}{Cu?en?2}(BW12O40)]?OH?·2H2O?Hpdc=2-picolinic acid,en=ethylenediamine??5?[{Cu5??pz?6?H2O?4}(BW12O40)]?6?Single-crystal X-ray diffraction studies shows that compounds 1-6 are based on[BW12O40]5-cluster anion.Compounds 1-2 are modified by silver ion.In compound 1,adjacent[BW12O40]5-cluster anions connected by{Ag?phen?}group constitute a double polymers.The adjacent structure unit through supramolecular interaction constitute one dimensional chain,two-dimensional and three-dimensional structure.In compound2,the[BW12O40]5-is as 8-connected node incorporated into the orifice of the Ag-pz framework forming the glamorous POM-based metal organic frameworks?POMOFs?.And the 3D POMOFs possess a kind of novel topology{42·54}2{44·512·68·73·9}{44·53·63}{44·55·6·74·9}{73}.In compound 3,adjacent structure unit constructed by[BW12O40]5-polyanion and{Cu?bim?2}are connected by hydrogen bonding to form a symmetrical structure.Two{{Cu?bim?2?H2O?}and a{Cu?bim?2}segment form a sandwich structure.The symmetrical structure and sandwich structure alternately form a one-dimensional chain by hydrogen bonding,and constitutes a three-dimensional structure through supramolecular role.Compound 4 is composed of{Cu?bipy?2}2{BW12O40}-and[Cu?2,2'-bipy?2]+which alternately connected by?-?stacking to form an infinite one-dimensional chain.And form the two-dimensional and three-dimensional structure of the ABAB arrangement through the supramolecular role.In compound 5,each new segment constructed[BW12O40]5-cluster anion and{Cu?Hpdc??en?}{Cu?en?2}connect with[Cu?en?2?H2O?]2+ion by the weak Cu-O bond forming a asymmetric unit.The asymmetric unit form a one-dimensional chain structure,a two-dimensional structure and a three-dimensional structure by supramolecular action.In compound 6,copper ions and pz ligands are alternately joined to form a two-dimensional Cu-pz layer which exists large cucurbit-likepores composed of12-nuclear metallamacrocycle{Cu?pz?}12.and then the adjacent chiral Cu-pz sheets are packed to a 3D POMOFs structure through[BW12O40]5-cluster anion.The synthesized compound were used as the active material of the electrode.In addition,[{Ag5?pz?7}(SiW12O40)]?OH?·H2O?7?and?Hpyr?[{Ag?pz?}2(PMo12O40)]?8??pz=pyrazine,pyr=pyrrole?synthesized in the previous group,with similarly structure and composition,have been studied comparatively.Their supercapacitors properties of synthesized compounds by cyclic voltammetry,charge/discharge studies,electrochemical cycle stability and electrochemical impedance studies have been investigated.The results showed that compounds 1-6 have redox peaks which all display pseudocapacitor.When used as electrode materials,as-prepared compounds have high specific capacitance above 500F g-1 at a current density of 2.16A g-1,higher than reported in the literature,the order of size is:compound 8>compound 2>compound7>compound 1>compound 5>compound 4>compound 3>compound 6.Ag-modified compounds have higher specific capacitance than Cu-modified compounds.and favorable cycling stability,after 1000 cycles,the retention rates of the capacitance are above 80%.The photocatalytic activity of the compounds were studied by the degradation of the RhB and MB as probe reactions.The results were shown in 90minutes,the degradation rate of MB were above 91%,and the degradation rate of RhB was above 90%in 150 minutes.It is indicated that the synthesized compounds havegood degradation effect on RhB and MB,and is a promising photocatalyst. |
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