In,Fe-based Metal-organic Frameworks (MOFs)Photocatalysts: Preparation, Characterization And Modification

Because of the advantage of mild reaction condition and non-secondary pollution,photocatalysis has been regarded as one of the most effective way to solve environmental pollutions and energy crisis.However,the conventional TiO2-based photocatalysts only be activated under UV light irradiation,which greatly restrict their application.Therefore,designing and seeking novel visible light photocatalyst with high activity is still a central challenge so far.Among various kinds of materials,Metal-Organic Frameworks(MOFs)have aroused a great interest due to their intriguing physicochemistry properties.MOFs are a new class of organic-inorganic hybrid solids with infinite three dimensional networks.Their unique properties such as high porosity,large specific surface area and structural flexibility have led to the successful application of MOFs in heterogeneous catalysis.However,the great potential of MOFs as photocatalysts is still not fully appreciated.This dissertation mainly focused on the development of efficient MOFs photocatalytic materials with tunable band structures and high stability.On one hand,we tuned the band structure of MOFs by modifying the ligand substituents and further the structure-photoactivity relationships of MOFs photocatalysis,which could help us to understand the intrinsic nature of photocatalysis from molecule level.On the other hand,in order to optimize the photocatalytic performance of MOFs materials,we introduced the functional entities into MOFs,which provide useful insights for synthesizing novel and efficient photocatalysts.The details are summarized briefly as follows:(1)The photocatalytic reduction of Cr(?)to Cr(?)under visible light irradiation was for the first time realized over a photoactive In-containing MOF,MIL-68(In)-NH2.The photoabsorption edge of MIL-68(In)-NH2 could be shifted to the visible light region by simply introducing the amino group on the organic ligand.(2)A simple and flexible electrostatic self-assembly strategy was developed to fabricate novel photocatalysts MIL-53(Fe)-RGO(M53-RGO).Such a strategy could make the two ingredients undergo a relatively adequate interfacial interaction.Therefore,the lifetime of photogenerated charge carriers could be improved much more effectively as compared to the simply random integration of RGO and MIL-53(Fe)via one-pot solvothermal method(D-M53-RGO).As a result,the M53-RGO exhibited improved photoactivities compared with the DM53-RGO.(3)Pd@MIL-100(Fe)was fabricated via a facile alcohol reduction approach and exhibited enhanced photocatalytic activity compared with the pristine MIL-100(Fe)towards the photocatalytic treatment of pharmaceuticals and personal care products(PPCPs).The higher photoactivity of Pd@MIL-100(Fe)could be ascribed to the synergistic effect of the enhanced light absorption intensity and increased surface area as well as the more efficient separation of the charge-carrier.(4)MIL-100(Fe)could not only serve as a host to control the encapsulation of H3PMo12O40,but also facilitate the separation of photogenerated charge carriers by forming the effective interfacial contact with H3PMo12O40 when the two components have well-matched band structures.The as-prepared samples were stable and able to serve as a promising photocatalyst for the selective oxidation of alcohols and reduction of Cr(VI)under visible light irradiation.In this dissertation,a series of novel MOFs photocatalysts were fabricated and applied to photocatalytic reactions,and their reaction mechanisms were also investigated in detail.The results may allow us to provide mechanistic and experimental guidance for understanding the nature of photocatalysis,developing highly efficient visible-light-induced photocatalysts and expanding the application range of MOFs in the field of photocatalysis.