Preparation And Properties Of Hybrid Materials Based On Polyoxometalates

Polyoxometalates?POMs?are widely used due to their diverse structures and unique properties.In recent years,POM-based hybrid materials have been broadly investigated.However,the application in photochromic and photothermal therapy is still no significant progress.In this thesis,we successfully synthesized two novel POM-based polymeric hybrid materials using hydrothermal method and studied their fascinating properties.We also fabricated porous WO3/C nano-octahedrons using the POM-based metal-organic framework materials as precursors,and studied their electrochemical performances.1.Preparation of POM/PVP hybrid materials and their property investigationWe prepared the H2W6O19/PVP and IH4Mo4O14/PVP hybrids using WCl6,MoCl5,polyvinylpyrrolidone?PVP?as raw materials by hydrothermal method.The structures and properties of the hybrids have been studied in details.The H2W6O19/PVP are blue-color powders in the solid state and can be stable in the air.Once dissolved in water,upon UV irradiation,the H2W6O19/PVP hybrids show ultrafast and reversible redox transformations with tunable acidities.The metal synthesis strategy using H2W6O19/PVP hybrids omits the photochemical or electrochemical reduction procedures since the POM clusters in the hybrids are stable in their reduced form.The H2W6O19/PVP-based rewritable paper can be facilely fabricated by coating a white commercial paper with the hybrids.As-obtained RP can be stable in aerobic conditions in either blue color reduced state or white color oxidized state.For the white RP,blue patterns can be photoprinted and for the blue color reduced RP,white patterns can be obtained through water-jet printing.The H4Mo4O14/PVP are yellow-color powders in the solid state,which have high solubility in water and the solution shows a stable blue color,and the H4Mo4O14/PVP hybrids show strong absorption in the near infrared region.The temperature of the H4Mo4O14/PVP hybrids solution can be increased from 20? to 54? by 808 nm laser irradiation,while most of the reports about photothermal therapy?PTA?for killing tumor cells usually needs a temperature of 40 ? to 45? so H4Mo4O14/PVP is a potential photothermal material that can be used in PTA.2.POMOF-Template preparation of porous WO3/C nano-octahedrons and Lithium-ion batteries performanceThe POMOF?MENU-3?was prepared by solvothermal method using Keggin phosphotungstic acid hydrate and Cu-based MOFs.Then we fabricated WO3/C by annealing NENU-3 and acid treatment.The phases and microstructures of WO3/C have been characterized.The porous WO3/C nano-octahedrons with a diameter of approximately 800 nm can be homogeneously dispersed,also the octahedron surfaces are rather rough.According to the N2 isothermal adsorption-desorption test,the specific surface area of WO3/C nanostructures was?164.45 m2 g^-1.Porous WO3/C structure as LIBs anode shows excellent specific capacity,high cycling stability and rate performance.At a current density of 100 mA g^-1m the first discharge capacity can be as high as 1463.4 mAh g^-1.Even at a high current density of 1200 mA g^-1.the discharge capacity can still be maintained at 256 mAh g^-1.