Transition Metal (Zn,Mn,Cu) Modulation Of UiO-66 Synthesis And Removal Of Ciprofloxacin

UiO-66,as one of the most stable metal-organic frameworks（MOFs）,has attracted a lot of attention in the field of adsorption and photocatalysis.However,the application of UiO-66 is still limited due to either the low accessibility of micropores or the poor electron-hole charge separation capability.The aim of this study is to investigate the role played by transition metals（Zn,Mn,Cu）in the modification of UiO-66 and to analyze the efficacy and mechanism of Zn/Mn/CuUiO-66 in the synergistic adsorption and photocatalytic processes using ciprofloxacin（CIP）as a test subject,as follows:（1）Transition metal doping and loading can promote charge separation to enhance photocatalysis.In this study,Zn-doped UiO-66（ZnUiO-66）and Mndoped UiO-66 catalysts（MnUiO-66）were prepared by a one^-step solvothermal method to investigate the effects of the introduction of Zn and Mn on the synthesis of UiO-66 catalysts and on the removal efficiency of CIP.The characterization results showed that Zn and Mn doping changed the surface morphology of UiO-66 and reduced the particles of ZnUiO-66 and MnUiO-66.The UV-vis diffuse reflection demonstrated that the introduction of Zn and Mn improved the absorption ability of UV light.X-ray photoelectron spectroscopy showed that the defect density of ZnUiO-66 was higher than that of MnUiO-66.The adsorption capacity and photocatalytic removal capacity of ZnUiO-66 were 5.40 and 3.67 times higher than those of UiO-66,respectively,and the efficiency of MnUiO-66 was 5.25 and 3.68 times higher than those of UiO-66,obtained by using CIP as the test object.The active group capture experiments showed that superoxide radical（·O₂^-）,hydroxyl radical（·OH）and hole（h⁺）were the main active species in the degradation process of CIP.（2）Defects are important adsorption and active sites,while being able to inhibit the complexation of electron holes.Therefore,we further constructed oxygen vacancies（OVs）and mesoporous defects by doping UiO-66 with Cu elements in this study,which improved the microporous mass transfer capacity of UiO-66 and promoted charge separation,demonstrating the ability to efficiently remove CIP from aquatic systems.First of all,denatured mesopore defects were produced in Cu doped UiO-66 which possessed a 58%increase in specific surface area compared to UiO-66,facilitating the adsorption of molecular oxygen.Secondly,Electron（e^-）was preferentially trapped by OVs under light irradiation.e^-reacted rapidly with the surface adsorbed oxygen to generate ·O₂^-.Meanwhile,copper incorporation increased the photocurrent and reduced the interfacial charge transfer resistance,thereby improving the charge separation efficiency.Compared with ZnUiO-66 and MnUiO-66,0.8CuUiO-66 has improved adsorption and photocatalytic performance in terms of CIP removal due to the presence of OVs defects and mesoporous defects with irregular pore structure during the synthesis of 0.8CuUiO-66.The adsorption efficiency and photocatalytic performance of mesopore Cu doped UiO-66 with OVs were 8.1 and 3.7 times higher than those of UiO-66,respectively.This study paved a way for the one^-step synthesis of MOFs containing OVs and broadened the possibilities of practical applications for photo-induced removal of antibiotics from effluent.