| Phosphomolybdenum polyoxometalates occupy a high position in polyacid chemistry and are an important branch of heteropolyacids.Keggin-type derivatives are currently the most widely synthesized and widely used heteropoly compounds.At present,the structure types of polyoxometalates are not limited to classic structures.Some non-classical types with novel structures show more excellent physical and chemical properties.As one of the representatives,basket-type polyoxometalates show outstanding advantages in the fields of light,electrocatalysis,magnetism,and energy storage.Number of hybrid materials.In this paper,four different cases of Keggin and basket-type phosphomolybdate were synthesized by adjusting different pH values,the types of soft and hard ligands,and the types of transition metals by hydrothermal synthesis.According to elemental analysis composition and single crystal X-ray diffraction analysis,their chemical formulas are determined as: （Hami）4[（VO）{PMo12O40}2]（1） {Sr（phen）3}2[PMoVMo11VIO40]（2） {CuI（pyr）2}[{CuI（pyr）2}3(PMoVMo11VIO40)]（3） [{Ag5（pz）6Cl}（PMo12O40）2]（4） （trz）[{Ni（bpy）（H2O）}4{SrP6Mo2VMo16VIO73}]·2H2O（5） （H2btb）2[{Cu（H2O）2（phen）}2Cu（H2O）2{SrP6Mo4VMo14VIO73}]·5H2O（6） （H4btb）[{Ag4（H2O）（pz）5Cl}{SrP6MoVMo17VIO73}]·4H2O（7） [{Na（H2O）（Hbtb）}{Cu3IICuI（H2O）（pz）5Cl}{SrP6Mo2VMo16VIO73}]·3H2O（8） (ami=2-aminopyridine,phen=1,10-phenanthroline,pyr=pyrazole,pz=pyrazine,bpy=2,2’-Bipyridine,trz=1,2,4-triazole,phen=phenanthroline,btb=1,4-bis（1,2,4-triazole butane）。Analysis by crystal structure:Compound 1 is a zero-dimensional Keggin structure modified by a transition metal vanadium cap and diaminopyridine;Compound 2 is a reduced Keggin supramolecular hybrid modified by the Sr（phen）3 complex;Compound3 is composed of{CuI（pyr）2}complex acts as a two-dimensional organic-inorganic hybrid layer extended by the linking unit;compound 4 is a three-dimensional metal woven from the rings formed by the alternating connection of six Ag and six pyrazine molecules as the basic unit A unique host-guest three-dimensional network composed of an organic host network and a two-node Keggin polyacid guest molecule.Compound 5is a four-supported zero-dimensional basket assembly modified by the{(Ni（bpy）（H2O）}complex;Compound 6 is a double-supported basket cluster modified by two{Cu（H2O）2（phen）}complexes The unit is a one-dimensional chain assembly of basic building blocks;Compound 7 is a 2DPOMOF structure with a unique metal-organic chain with a long arm and a polyacid as the node;Compound 8 is a 2DPOMOF similar to Compound 7 extended under the action of Na bridge The resulting three-dimensional basket assembly with large micropores.Compound 8 represents the first three-dimensional basket phosphomolybdate assembly.The capacitance properties of compounds 1-8 as erbium electrodes were studied.The specific capacitances of compounds 5-8 are higher than those of compound 1-4.Comparative experimental results show that the specific capacitance of compound 4(701.9F g-1)and the specific capacitance of compound 8(1746 F g-1)are the same at the same current density.Experiments have found that the cyclic stability of high-dimensional compounds is the best.This is because in three-dimensional compounds,the transition metal type promotes the transfer of electrons and ions and improves the electron transport efficiency.Large-dimensional holes in the structure of high-dimensional compounds also provide larger transmission space and increase the specific surface area of the material.Large,the specific capacitance also increases,and the rate performance is relatively better.The compound 1-8 phosphomolybdate hybrid material has a dual-function catalytic effect on both hydrogen peroxide and bio-organic molecule ascorbic acid,and is a potential dual-function sensor material.The high-dimensional compounds4 and 8 have better catalytic effects than the zero-dimensional ones,which may be due to the acceleration of the proton and electron transport efficiency by the metal-organic complex network.Compounds 1-8 have good photocatalytic activity against methylene blue（MB）and rhodamine B（RhB）,which are common dyes in wastewater under ultraviolet light irradiation.Experiments show that the catalytic effect and degradation time of high-dimensional compounds are both Better than zero-dimensional compounds,and the degradation of basket-type compounds is significantly better than Keggin-type compounds.It is possible that the type of the metal-organic ligand and the large hole in the center of the basket-type compound are favorable for the separation and migration of electrons and holes in the photocatalytic process. |
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