Synthesis And Photocatalytic Properties Of MOF Based Complexes

The metal organic framework（MOF）compound is a promising photocatalyst.It is a new type of crystal material formed by self-assembly of organic ligands and metal ions or metal clusters through coordination bonds.Due to its high porosity,large specific surface area and easy functionalization,MOF has been applied to many fields such as multiphase catalysis,sensors,gas adsorption and drug delivery.However,using MOF alone as a photocatalyst still has the disadvantages of low light absorption efficiency and high carrier recombination rate.Therefore,it is necessary to take effective ways to improve its photocatalytic efficiency.The combination of MOF and another material to construct a MOF-based composite photocatalyst can take advantage of their synergistic effect to improve the photocatalytic efficiency.This thesis starts with the construction of new characteristic MOF-based composite photocatalysts and the exploration of their application in the photocatalytic transformation of organic matter.Using zirconium-based metal organic framework NNU-28（[Zr₆O₄（OH）₄（L）₆]?6DMF）as the carrier,the semiconductor material was combined with it.And two composite photocatalysts with visible light absorption ability have been successfully synthesized.The structure and property of the composites were analyzed by means of powder X-ray diffraction,infrared spectroscopy and solid state ultraviolet spectroscopy,and they were used as photocatalysts to explore the property of photocatalytic organic conversion reactions.The main research contents are as follows:1.By simple solvothermal method,different amounts of graphite phase carbon nitride（g-C₃N₄）were combined with metal organic framework NNU-28 to synthesize Zr-MOF/g-C₃N₄ composites with different doping amounts of g-C₃N₄.The synthesized composites have good visible light absorption ability and they are potential photocatalyst materials.Using the synthesized composite materials as the photocatalysts and methyl phenyl sulfide as the model substrate,we explored the property of the photocatalytic reaction of thioether under visible light irradiation.Studies have shown that the composite photocatalyst has enhanced photocatalytic activity compared to its components g-C₃N₄ and Zr-MOF.The synthetic material has certain universality for the oxidation reaction of sulfide compounds.Under the same conditions,a variety of sulfide compounds can be converted into corresponding sulfoxide products with high selectivity.The mechanism study shows that singlet oxygen（¹O₂）and superoxide radicals(O₂^·-)produced in the process of light-excited Zr-MOF/g-C₃N₄ act as active oxygen species to promote the reaction.2.Taking NNU-28 as the carrier,the semiconductor material CdS was composited with it.Zr-MOF/CdS composite photocatalysts with different CdS contents were constructed,and the synthesized composites exhibit good visible light absorption capacity.We used the synthesized composite materials as photocatalysts and explored their photocatalytic property for the coupling reaction of benzylamine.The experimental results show that it has a higher catalytic activity for the photocatalytic oxidation of benzylamine,which is significantly higher than the composite components Zr-MOF and CdS.Cyclic experiment shows that the composite photocatalyst we synthesized can still maintain a high conversion rate and selectivity in the reaction after repeated use,it is recyclable.Mechanism study further shows that singlet oxygen（¹O₂）and superoxide radicals(O₂^·-)together act as the active oxygen species in the photocatalytic reaction.