| Iodine is a necessary nutrient for the human body,known as intelligence element,which has the function of maintaining the normal metabolism and life activities of the human body.Its chemical products were widely used in medicine,agriculture,industry and other fields.However,the iodine content in nature is low,which makes it difficult for iodide ions to be oxidized into simple iodine in a short time.Therefore,it is necessary to improve the oxidation rate of iodide ions by using suitable catalysts.Polyoxometalates（POMs）were widely used in the field of catalysis because of its simple preparation,high catalytic activity,high selectivity and no pollution to the environment.However,its high solubility in aqueous solution makes it only used as homogeneous catalyst in the system,which is difficult to separate and recover.It is an effective way to realize heterogeneous polyoxometalate by linking polyoxometalate with suitable organic components to form organic-inorganic hybrid compounds.Polyoxometalates can act as electron acceptors to bind many organic components containing N and O.These compounds can be used as ideal industrial catalysts through synergistic interaction between organic and inorganic components.In this paper,a series of polyoxometalate-based organic-inorganic hybrid compounds modified by N-containing and O-containing organic ligands were synthesized by hydrothermal method.These compounds were characterized by IR,XRD,TG,X-ray single crystal diffraction,SEM and the element analysis and used as a catalyst for the reaction of iodide ion peroxidation.Through experimental research,the main conclusions are as follows:1.Using 1,3-bis（4-pyridyl）propane and benzimidazole as organic parts,two organic-inorganic compounds based on Keggin type polyoxometalates were obtained.In compound 1,the organic ligand and multiple anions are combined through proton transfer and hydrogen bonding to form a one-dimensional chain along the b axis,which is parallel to each other and forms a two-dimensional layered structure parallel to the ac plane.Finally,the three-dimensional structure is expanded through the hydrogen bonding between layers.Compound 2 is a three-dimensional supramolecular structure constructed by bpp.The organic components and polyoxometalates are connected by electrostatic,π-πstacking and hydrogen bonding.The results of catalytic performance showed that the two compounds had better catalytic activity,and the catalytic activity of compound 2 was slightly better than compound 1 under the equal situation.It is noteworthy that homogenization occurs in both catalysts,which can be attributed to the weak interaction between organic components and polymolybdate in both catalysts.(PMo12O40)(C13H16N2)2·2H2O（1）(PMo12O40)（C7H7N2）4·2H2O（2）2.An organic-inorganic hybrid was obtained from 3-amino-1,2,4-triazoles and polymolybdate.In compound 3,copper is coordinated with the N atom of the organic ligand and the oxygen atom at the end of the heteropoly anion to form the basic unit structure,and the basic unit structures are connected to each other through hydrogen bonds to form the3D molecular structure.It showed good catalytic activity and recyclability in catalytic iodide oxidation reaction.XRD and SEM tests showed that its structure had not changed before and after catalytic reaction.[2(C6H12Cu3Mo12N12O40P)]·H2O（3）3.An organic-inorganic hybrid was synthesized by in situ decarboxylation of 2-picolinic acid as pyridine ring at high temperature and pressure with Keggin polymolybdate.Compound 4 is a three-dimensional supramolecular structure formed by hydrogen bonding,π-πstacking and electrostatic interaction between pyridine rings and polymolybdenum anions.The transition metal exists as an anticharged ion.The catalytic results of compound 4 showed that the oxidation rate of iodide ion by hydrogen peroxide reached 2.41×10-5 mol·L-1·s-1 at T=55℃,p H=1.0,c（I-）=2.5×10-3 mol·L-1,and c（H2O2）=2.0×10-3 mol·L-1.Compared with the reaction system without catalyst,the compound increased by 1839.7 times,and it showed a certain recyclable performance in catalytic reaction.(PMo12O40)（C5H6N）3（4）... |
