Regulation Of Acidity And Pore Structure Of UiO-66 And Catalytic Performance Of Pt/UiO-66

Metal–organic frameworks?MOFs?,which are constructed from the assembly of metal ions or metal clusters with organic linkers,represent a new class of crystalline porous materials.MOFs have shown potential applications in the fields of gas storage and separation,drug delivery and heterogeneous catalysis,among which catalysis is one of the fastest-growing segments.The applications of MOFs in heterogeneous catalysis field focus on three main parts.First,the specific catalytic active sites or post-grafted functional groups on MOFs can be directly used as independent catalysts.Second,MOFs can be acted as the sacrificial templates to fabricate a variety of?heteroatoms-doped?carbon-based nanomaterial.Third,MOFs can be used as support materials,distributing the metal nanoparticles on the inner surface and outer surface of MOFs?denoted as M/MOFs?.In this thesis,the works mainly focus on MOFs supported metal catalysts.UiO-66,assembling Zr₆O₄?OH?₄ octahedron with1,4-benzendicarboxylic acid,has been the most popular and promising MOF support due to its high thermal and chemical stabilities.For UiO-66 supported metal catalysts,the acidity and pore structure of UiO-66 support are two important factors affecting the catalytic performance of the resulting catalysts.However,the affects are rarely reported about the acidity of UiO-66.Moreover,UiO-66 prepared by traditional method is microporous,which inherently hinder the diffusion of bulky molecules and limits their interactions with the active sites within MOF structures.In view of the deficiencies,we have carried out the following work:?1?Tuning acidity in UiO-66 supports through defect engineering.A series of UiO-66 supports with different acidity were synthesized.NH₃-TPD results reveal that the acid amount in each UiO-66 is consistent with their defect amount.The catalyst of Pt NPs combined with different acidic UiO-66 supports shown different catalytic performance.In the case of the optimum preparation and reaction conditions,the selectivity to COL can reach 96.3%.It indicates that it is a effective strategy to adjust the acidity of UiO-66 support by defect engineering and improve the selective hydrogenation of cinnamaldehyde over Pt/UiO-66 catalysts.?2?Hierarchical UiO-66 supports were successfully synthesized by introducing a suitable amount of water into the conventional synthesis of UiO-66 without the need for a chelating agent,surfactant or aging.Comparison with microporous Pt/UiO-66-M,the hierarchical Pt/UiO-66-HP catalysts exhibited significantly enhanced catalytic activity in the hydrogenation of naphthalene reactions.It indicates that the construction of hierarchical structure can effectively improve the catalytic performance of hydrogenation of naphthalene reactions.