Synthesis,Modification And Catalytic Application Of Metal-organic Frameworks

Metal-Organic Frameworks(MOFs)are crystalline materials which hybridized between metal nodes and organic linkers.Due to the adjustable compositions on MOFs resulted in tunable structure and their properties which existed great value in varieties of applications including adsorption,separation,and catalysis,etc..Therefore,the structure design,synthesis,modification,characterization of MOF materials and further in their application for catalysis reaction,are mainly described on herein research thesis.Moreover,the investigation in structural properties of the synthesized and/or modified materials interacted to catalytic model reactions,are deeply studied and illustrated.The research contents of this thesis are following:A core-shell structure metal-organic framework based on the Zr clusters bridging with H₂bdc linker(UiO-66)as a core-structure and H₂bpydc linker(UiO-67-BPY)as a shell-structure was developed(UiO-67-BPY@UiO-66).The combination of several techniques such as XRD,FTIR,SEM,TEM,and surface area analysis etc.were applied for characterization and confirmed a core-shell structure of UiO-67-BPY@UiO-66.Taking advantage of the high porous stability of the core-structure(UiO-66)and the presence of active Lewis basic sites from the bipyridinic linker in the shell layer(UiO-67-BPY)could be advantageous for basic-catalyzed reactions.The synthesized core-shell material was applied as a heterogeneous catalyst for the Knoevenagel condensation as a model reaction.An excellent catalytic performance was obtained by the core-shell material over traditional MOFs(UiO-66,UiO-67-BPY)and other previous reports based on MOFs.The excellent dispersion of the active sites(Lewis basic)in the outer layer of the designed core-shell structure was a breakthrough to prevent mass diffusion limitation during catalysis.Additionally,the catalyst can be recycled and maintaining its high catalytic performance at least 4 times.The as-synthesized core-shell UiO-67-BPY@UiO-66 was subjected to metallization treatment.Silver(Ag)was selected for the selective metal incorporation and an excellent Ag-dispersion via coordination with the bipyridinic groups in the UiO-67-BPY layer of the core-shell material was obtained from the proof of ICP,XPS,EDS.The synthesized material(Ag-UiO-67-BPY@UiO-66)was successfully applied as a heterogeneous catalyst for the CO₂ fixation via carboxylation of terminal alkynes.The catalytic material showed excellent yields using at a low Ag-loading under mild reaction condition(50?C,1 bar).Moreover,the catalyst can be recycled for at least 5 times maintaining a stable catalytic performance.Interestingly,the high catalytic activity of the synthesized material demonstrated clearly the beneficial advantage of the metalated core-shell structure over the reported routes to synthesize silver catalysts such as encapsulated Ag nanoparticles(AgNP@MOF)or Ag-bidentately coordinated on traditional MOFs applying the same reaction model.The core-shell UiO-67-BPY@UiO-66 was metalized with bisdichloropalladium(?)to obtain the Pd-UiO-67-BPY@UiO-66 material.The material characterization via ICP,EDS,SEM,XPS,porosity and surface analysis,etc.,confirmed that palladium(Pd)species were incorporated into the core-shell MOF@MOF after metallization methods.Moreover,the metal species analysis by XPS proved that divalent Pd species existed as homogeneous rather than Pd nanoparticle in the synthesized Pd-UiO-67-BPY@UiO-66.The hydrogenation of olefins was selected as a model reaction to determine in the catalytic performance of materials.The result revealed that Pd-UiO-67-BPY@UiO-66 possessed high catalytic activity,and catalyst also could be reused at least 3 recycle times with maintaining high catalytic activity.Furthermore,the Pd-UiO-67-BPY@UiO-66 catalyst exhibited high stable reactivity in various olefin substrates and even achieved high conversion in short reaction time.