| Basket-type phosphomolybdate,as an important non-classical polyoxometalate,is a polyacid compound formed by introducing metal atoms such as K,Sr,Ba,and La as templates.It has two valence states of MoV and MoVI,so it has the phenomenon of mixed valence delocalization,and its band gap range is not much different from that of semiconductor materials,which is between 2.7-3.2 e V.It is widely used in the field of electrochemistry.Different from the classical polyacids,the intermediates of the basket-type phosphomolybdate compounds are very unstable,so they cannot be synthesized by the precursor method,and the large steric hindrance also limits the synthesis of new compounds.Basket-type compounds are less studied.In this paper,six new basket-type phosphomolybdates were synthesized by one-step hydrothermal method,introducing appropriate transition metals and suitable nitrogen-containing organic ligands,and taking advantage of the bridging effect of transition metals and the coordination ability of organic ligands.compounds,and the structures and molecular formulas of compounds 1-6 were determined by structural analysis means such as elemental analysis,infrared absorption spectrum,thermogravimetric analysis and single crystal X-ray diffraction.(H2bpp)4[Co(H2O)2{Sr(?)HP6Mo18O73}2])(1){FeIII(phen)3}4[FeII{Sr(?)P6Mo?17Mo?O73}2]2H2O(2)(H2bipy)8(H2biyb)5[Na{Sr(?)P6Mo?17Mo?O73}2]2)(3)(H2bib)4[{Cd(H2O)2}{Cd(H2O)2}2{Sr(?)P6Mo?17Mo?O73}2])(4)(bzi)2(H2bipy)[{Na Cd(H2O)2Cd(H2O)4}]{Sr(?)P6Mo?17Mo?O73})(5)(HDMAP)2[{Cd(H2O)2}2]{Sr(?)P6Mo18O73}}·6H2O)(6)(bpp=1,3-Di(4-pyridyl)propane,phen=1,10-Phenanthroline,bipy=4,4'-Bipyridyl,biyb=1,4-Bis(imidazol-1-ylmethyl)benzene,bib=1,4-bis(imidazol-1-yl)butane,bzi=Benzimidazole,DMAP=4-Dimethylaminopyridine)Crystal structure analysis shows that compounds 1-3 are dimer clusters formed by Co(H2O)2,FeII,and Na as connecting units,respectively,but they are different.Compound 1 is staggered by extending ABAB The 1-D chains and 2-D layers formed a supramolecular network with a pore structure.Compounds 4-6 are all 1D chain structures formed by Cd as the linking metal,but modified by protonated bib organic ligands,protonated bipy and biz organic ligands,and protonated DMAP organic ligands,respectively.Na in compound 5 also participates in dimension expansion as a bridging unit.Compounds 1-6 were ground with acetylene black respectively,and ethanol and Nafion solution were added to make glassy carbon electrodes,which were tested for cyclic voltammetry,electrocatalytic oxidation of ascorbic acid,and electrocatalytic reduction of hydrogen peroxide,respectively.The test results show that compounds 1-6have good catalytic performance for both AA and H2O2,thus indicating that compounds1-6 are potential bifunctional catalytic materials.It may be due to the better effect of 1D chain-like compounds on the conduction of electrons.The photocatalytic test results of the compounds show that the six compounds have excellent degradation effect,high cycle stability and service life on the common chemical organic dyes MB,Rh B,MO and AP in sewage.The photodegradation pathway of compound 1 to four dyes was studied,and the results showed that the three active substances h+,·O2-and·OH played different roles in different reactions,which proved that the photodegradation pathway between the four dyes was is different.In addition,compared with other compounds with classical polyacid structure,the degradation efficiency of basket-type compounds is higher.The reason is that basket-type compounds have a cage-like structure,and this special structure can greatly accelerate the rate of electron transport.Among them,the degradation effect of compound 4-6 is better than that of compound 1-3,which is due to the one-dimensional chain structure formed by metal bridging in compound 4-6,which increases the basket size.The specific surface area increases,and the contact area between the active material and the organic dye increases,so the active sites for redox reactions will increase,and the time required to degrade the same dye will be shorter.Therefore,the contribution of basket-type phosphomolybdate in the photocatalytic degradation of organic dyes cannot be ignored. |
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