Preparation And Characterizati On Of Keggin Cluster-based Functional Materials

Polyoxometalates（POMS）are anionic molecules with high negative charge,high molecular weight and good solubility in polar solvents.Due to the diversity of its structure,it has shown excellent performance,so it can be widely used in biochemistry,catalysis,medicine,material science and other fields.In this paper,five Keggin type functional materials with novel structure and excellent performance were synthesized by hydrothermal synthesis technology,by selecting appropriate raw materials,controlling reaction time,temperature,p H and oxidation environment.The structural characteristics of IR,UV-Vis,XRD,XPS and TG were characterized by elemental analysis and X-ray single crystal diffraction.Their functional properties in photocatalysis and chemical catalysis were studied.1.Three kinds of Keggin type cluster functional materials with extended stru-cture oftransitionmetalcomplexesweresynthesized:[Cu（en）₂（H₂O）]₂{[Cu（en）₂][{Cu（en）₂}₂Si W₁₁Cu O₃₉][{Cu（en）₂}Si W₁₁Cu O₃₉]}·6H₂O（1）{K（H₂O）₂[Cu_0.5（en）][Cu Si W₁₁O₃₉]}（H₂en）₂（2）[Zn（phen）₂]₂[Si Mo₁₂V₂O₄₂][Zn（phen）₂（H₂O）]₂[Si Mo₁₂V₂O₄₂]（C₅NH₅）·2H₂O（3）（en=ethylenediamine,phen=phenanthroline,C5NH5=pyridine）.Compounds 1 and 2 are lacunary Keggin type functional materials substituted by transition metal Cu.The rare com-pound 1 is a dimer with different transition metal modified cluster anions as the building structural unit,and it is connected into a two-dimensional layered structure by the transition metal complex cation[Cu（en）₂]²⁺and the end oxygen bridge of cluster anions;Compound 2 is a kind of one-dimensional chain with Keggin type cluster anions connected by alkali metal K⁺and transition metal complex cation[Cu（en）₂]²⁺,between which a three-dimensional supramolecular network is connected by water molecules.Compound 3 is a double cap Keggin type cluster functional material.Two Keggin type vanadium-molybdenum oxygen clusters（POM1 and POM2）with two v-capped are used as structural units.The two cluster units are respectively connected with the complexes cation[Zn（phen）₂（H₂O）]²⁺,and[Zn（phen）₂]²⁺in the form of covalent bond and hydrogen bonding to form two-dimensional layered structure and two-dimensional supramolecular structure.Different two-dimensional layers are connected into three-dimensional supramolecular network by hydrogen bonds.2.Two Keggin type cluster hybrid materials with 2-aminopyridine as organic ligand were synthesized.[H₃PMo₁₂O₄₀]₂[C₅H₆N₂]₆（4）and[H₂PMo₁₂V₂O₄₂][C₅H₆N₂]₅·3H₂O（5）（C₅H₆N₂=2-pyridylamine）.Compound 4 and compound 5 arediscrete structures.Compound 4 is connected by two Keggin type cluster anions[PMo₁₂O₄₀]^3-via hydrogen bond to form a three-dimensional inorganic supramolecular network,and 2-aminopyridine molecules are filled in the pores;The novelty of 5 is that three water molecules form（H₂O）₃trinuclear water clusters.The water clusters are connected by hydrogen bonds to the two-capped Keggin-type cluster anions[PMo₁₂V₂O₄₂]^2-forming a three-dimensional inorganic network,2-aminopyridine filled in the void.There areπ...πstacking interactions between molecules to make the structure more stable.3.At room temperature,the catalytic activity of 1,3,4 and 5 was studied through the experiment of styrene epoxidation,and the photocatalytic degradation of 2 was studied by using Rh B to simulate the organic pollutants in industrial wastewater.