Study On The Preparation And Photocatalytic Properties Of UiO-66（Ce） And Its Composites

MOFs are the metal-organic frame materials with porous structure assembled by organic ligands and metal ions,with rich metal active sites and high porosity.MOFs are widely used in catalysis,gas adsorption and storage,sensing and drug delivery.Ce as a rare earth element,which content in the earth’s crust is relatively high but with low cost.Photostable Ce-MOFs combine the large specific surface area and dimensional selectivity of MOFs,which can be used as an excellent photocatalytic material.This paper mainly studied the photocatalytic degradation performance of UiO-66（Ce）on antibiotics.In addition,in view of the problem that UiO-66（Ce）is difficult to recycle as a powder photocatalyst.In this work,UiO-66（Ce）is loaded on a flexible-base aramid fabrics,which can realize recycling without affecting its photocatalytic activity,and has a considerable application prospect in practical applications.In this paper,two different UiO series MOFs materials were prepared,UiO-66（Zr）was prepared by solvothermal method,UiO-66（Ce）was prepared by direct reaction in solution.The structure and surface morphology were characterized by infrared spectroscopy,XRD and SEM.The UV-visible diffuse reflectance spectrum was used to test the absorption performance of the UiO-66（Ce）for UV-visible light,it showed that the band gap width of UiO-66（Ce）was2.85 e V,the valence band position was+2.2 e V,and the conduction band position was-0.65 e V by combining formulas calculation.Tetracycline and doxycycline were tested as simulated contaminants for their photocatalytic degradation performance,and the results showed that the photocatalytic degradation capacity of UiO-66（Ce）was much higher than that of UiO-66（Zr）.At the same time,the effects of different p H values and different catalyst dosages on photocatalytic degradation of antibiotics were studied.The results showed that the photocatalytic degradation rate of 20 mg/L tetracycline could reach 93.33%within 1 hour when the p H was 7 and the dosage of UiO-66（Ce）was 0.3 g·L^-1.The photocatalytic degradation rate of doxycycline was 92.71%when the dosage of UiO-66（Ce）was 0.2 g·L^-1.The photocatalytic degradation mechanism of UiO-66（Ce）was studied by free radical capture experiments.It indicated that superoxide radicals and photo generated holes were the main active substances.To realized the recycle of UiO-66（Ce）,the original aramid fabric was treated by alkali,and then the UiO-66（Ce）@aramid fabric was prepared by loading UiO-66（Ce）on the surface of the aramid fabric,using terephthalic acid and cerium ammonium nitrate as raw materials through layer-by-layer self-assemble method.The surface morphology and structure of the UiO-66（Ce）@aramid fabric were characterized by infrared spectroscopy,XRD,SEM and EDS.The results showed that the alkali-modified aramid fabric had a significantly higher load rate on UiO-66（Ce）than the untreated aramid fabric,100-200 nm UiO-66（Ce）nanoparticles were densely packed on the surface of modified fabrics.The photocatalytic degradation performance of UiO-66（Ce）@aramid fabric prepared with different self-assembly times was studied,and the results showed that the photocatalytic degradation rate increased with the increase of self-assembly times.The UiO-66（Ce）@aramid fabric assembled 20 times（3 cm×3 cm）had a photocatalytic degradation rate of 92.68%for 20mg/L tetracycline and 93.19%for doxycycline in 90 min.After 5 times recycle degradation with UiO-66（Ce）@aramid fabric,the degradation efficiency still remained above 85%,which meant that UiO-66（Ce）@aramid fabric had good recycle ability.