Research On The Preparation And Performance Of Carbon Dot-metal Organic Framework Composite

As a new type of light-emitting material,carbon dots（CDs）have good physical and chemical properties,which will be widely used.In addition,there are many types of fluorescent probes,which can be used in the fields of chemical sensing,biomedicine,analysis and detection.With the continuous deepening of research,people’s understanding of metal organic framework materials（MOFs）has deepened,and their unique physical and chemical characteristics have been widely used in gas storage,catalysis,biomedicine,chemical sensing and other fields.In this thesis,CDs@Zr-MOFs and CDs@Hf-MOFs composites were successfully synthesized by loading carbon dots on zirconium-based and hafnium-based metal organic framework materials,respectively,for fluorescence detection of hexavalent chromium in wastewater.In this thesis,CDs@Zr-MOFs composites were successfully synthesized by loading CDs on Zr-MOFs,and their chemical structures were characterized by scanning electron microscopy,infrared spectroscopy,and X-ray diffraction.The thermal stability of CDs@Zr-MOFs and The specific surface area was analyzed,and the composite has good thermal stability and high specific surface area.The fluorescent test proved that the material has good salt stability and pH stability.The experiment of fluorescence detection of Cr⁶⁺shows that:adding different metal ions to it,the fluorescence intensity of the material remains basically unchanged,and only has a significant response to Cr⁶⁺,indicating that the ion selectivity is high.Cr⁶⁺can cause fluorescence quenching of CDs@Zr-MOFs materials,and the detection limit is 0.235μM,which is far lower than other fluorescence sensors that detect Cr⁶⁺.The experimental mechanism of fluorescence detection of Cr⁶⁺shows that the fluorescence intensity and Cr⁶⁺concentration of CDs@Zr-MOFs material are in accordance with the Stern-Volmer equation,and the quenching constant(K_SV)is 0.0107μM^-1.In addition,we synthesized CDs@Hf-MOFs composites.The structure of CDs@Hf-MOFs composites was characterized by scanning electron microscopy,infrared spectroscopy,and X-ray diffraction.The thermal stability and BET specific surface area of CDs@Hf-MOFs were characterized by thermogravimetric curves and N₂adsorption-desorption.Analysis shows that the composite material has good thermal stability and high specific surface area.Fluorescence test experiments show that the material has good salt stability,pH stability and ion selectivity.Cr⁶⁺can cause fluorescence quenching of CDs@Hf-MOFs materials,and the detection limit is 0.251μM.The experimental mechanism of fluorescence detection of Cr⁶⁺shows that the fluorescence intensity and the concentration of Cr⁶⁺of CDs@Hf-MOFs material conform to the Stern-Volmer equation and the quenching constant(K_SV)is 0.01265μM^-1.