Synthesis And Photoelectrocatalytic Performance Of Heterostructure Metal Organic Framework Compounds

Metal-organic Frameworks(MOFs)is considered as one of the most potential photocatalyst materials because of its clear pore structure and controllable physical and chemical properties.Compared with the traditional inorganic photocatalyst materials,there are huge catalytic sites in MOF materials,among which Cr based MOF has attracted much attention due to its excellent performance.However,the high band gap energy limits the application of MIL-101(Cr)in the field of photocatalysis.In contrast,upconversion nanoparticles(UCNPs)with multi-level and narrow band gap quantum dots(CdSe)are promising candidates for the fabrication of composite photocatalysts.In this paper,the upconversion nanoparticle NaGdF4:Yb,Er and CdSe was be used to fix on the MOF material MIL-101(Cr).Through the cooperation of the two,the former can make the heterostructure have the ability of fluorescence regulation and improve the ability of UV response,while the latter can change the band gap width of the composite through the migration of electrons and holes.Both methods can make the hetero-structure composite show the highest photo-current intensity and the best photo-current rhodamine(RhB)degradation ability.1.A kind of MOF material(MIL-101(Cr))with octahedral pore structure was rapidly and efficiently prepared by hydrothermal method.This MOF material has regular structure,uniform size and strong adsorption,which makes upconversion nanoparticles(UCNPs)stably and evenly distributed on the surface of MIL-101(Cr),and a composite photocatalyst of MIL-101(Cr)/UCNPs with good structure was obtained.The synergistic effect of the two heterostructure materials makes the carrier MIL-101(Cr)more effectively absorb and utilize UV light,and to a certain extent expand the UV absorption range.The surface loaded up conversion nanoparticles can not only enhance the UV absorption ability of the composite,but also effectively separate the photogenerated electrons and holes(PG e~--h~+)under the UV response,and delay its recovery.Therefore,the photocatalytic ability of MIL-101(Cr)/UCNPs was improved.In addition,the up-conversion fluorescence intensity of the composite photocatalyst was regulated by adjusting the ratio of UCNPs and MOF.Finally,the influence of different doping amount of UCNPs on the catalytic ability of the composite photocatalyst was studied,and the optimal loading amount was found.2.As a typical II-VI group compound,CdSe has a low band gap width at room temperature.It is a N-type semiconductor material,which has an energy band structure that can directly transition and almost responds to the whole visible spectrum.According to the photocatalytic mechanism,the narrow band gap semiconductor CdSe has potential value as a high-quality photocatalyst.In this thesis,we have prepared CdSe quantum dots and metal organic framework material MIL-101(Cr)respectively,and loaded the narrow band gap semiconductor photocatalysis material CdSe quantum dots onto the surface of MIL-101(Cr)by two steps,forming stable heterogeneous structure composite materials CdSe@MIL-101(Cr)The combination of the CdSe and the MIL-101(Cr)can improve the photocatalyst's photoresponse ability by changing the band gap width of the composite.The photocatalysis ability of the composite was improved by enlarging the absorption range of photocatalyst,and the catalytic performance was observed by the degradation of RhB dye.