Preparation Of Metal-organic Frameworks UiO-66-NH₂（Zr/Hf） And Piezoelectric/photocatalytic Degradation Properties

Dye wastewater mainly comes from the dye production and textile industry,which shows deep color,high turbidity,strong toxicity and so on.The arbitrary discharge of dye wastewater destroys the ecological environment and seriously affects human survival and life.Faced with such a dilemma,how to achieve efficient and harmless treatment of dye wastewater has become a hot research topic for researchers.At present,there are countless treatment methods for dye wastewater,which can be roughly divided into physical treatment,biological treatment,and chemical treatment.Chemical treatment methods（such as,photocatalytic oxidation,piezoelectric catalytic oxidation,and chemical oxidation）have become a focus of research as green and efficient dye wastewater treatment technologies.Metal-Organic Frameworks have attracted much attention due to their excellent physical and chemical properties and low preparation costs.The series of UiO-66-NH₂Metal-Organic Frameworks have been successfully applied in fields such as photocatalytic hydrogen production and dye wastewater degradation.However,the photocatalytic performance is poor due to low light utilization and rapid recombination of photo generated electron hole pairs.Researchers have proposed some methods（such as,ion substitution）to form framework materials with piezoelectric properties and improve the catalytic performance of the framework materials by utilizing the built-in electric field of piezoelectric materials to promote the separation of photo generated electron hole pairs.Therefore,searching for piezoelectric and semiconductor properties Metal-Organic Frameworks will greatly promote their development and application in the field of dye wastewater degradation.Metal-Organic Frameworks UiO-66-NH₂（Zr）and UiO-66-NH₂（Hf）were prepared by a solvothermal method from this starting point in this article.These were characterized by XRD,SEM,AFM,PFM,and UV-vis DRS,and the piezoelectric catalytic and piezo-photocatalytic degradation performance of Metal-Organic Frameworks for dye wastewater was deeply studied.The adsorption performance of UiO-66-NH₂（Zr）nanomaterials was studied.The removal rate of Rh B dye molecules could reach 89%within 120 minutes and the addition amount 60 mg;In order to achieve the degradation of dye molecules,piezoelectric catalytic degradation experiments were conducted.The results showed that the degradation rate of UiO-66-NH₂（Zr）nanomaterial of Rh B dye molecules could reach 80%within 20 minutes and the addition amount 18 mg,and the kinetic curve of the piezoelectric catalytic degradation process followed the first-order Langmuir-Hinshelwood model.The Zr ion of UiO-66-NH₂（Zr）nanomaterial was replaced by Hf ion to prepare UiO-66-NH₂（Hf）nanomaterial.The obtained UiO-66-NH₂（Hf）nanomaterial exhibits strong photo and piezoelectric responses,and its photocatalytic,piezoelectric,and piezo-photocatalytic properties were explored.A photocatalytic dye molecular degradation efficiency（62%）of UiO-66-NH₂（Hf）nanomaterial was achieved within120 minutes and the addition amount 18mg;The photocatalytic performance has been greatly improved by utilizing the piezoelectric properties of the material,and achieved piezo-photocatalysis.the degradation efficiency of Rh B dye molecules can be as high as 91%within 60 seconds and the addition amount 18 mg under ultrasound and light conditions.This paper explores the piezoelectric catalytic mechanism of UiO-66-NH₂（Zr）nanomaterials and the piezo-photocatalytic mechanism of UiO-66-NH₂（Hf）nanomaterials,and identifies the active species that play a key role in degradation during the experimental process.This article provides new ideas and methods for the research and exploration of this type of framework material in the degradation of dye wastewater by piezoelectric catalysis and piezo-photocatalysis.