Systematical Post-Synthetic Approaches to Tailoring the Structure of Metal-Organic Frameworks

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Systematical Post-Synthetic Approaches to Tailoring the Structure of Metal-Organic Frameworks
Other Titles
금속 유기 골격체의 구조변화를 위한 체계적인 합성 후 처리에 관한 연구
Park, Sungbin
Moon, Hoi Ri
Issue Date
Graduate School of UNIST
Metal-Organic Frameworks (MOFs), also known as Porous Coordination Polymers (PCPs) have been studied recently, in perspective of synthesis advanced structures. Since MOFs have defined structure with metal cluster and organic linkers, it is easy to modify its structures by the control in molecular level. Therefore, study about the structure of MOFs, especially in terms of, tailoring the structure of MOFs are an important issue. In this thesis, structure change, especially dimensional change of MOFs observed by Single Crystal X-Ray Diffraction (SCXRD) and core-shell MOF observed by Electron Microscopy (EM) was studied for tailoring structure via post-synthetic approaches. We synthesized a MOF and transform its structure via radiating 365 nm wavelength of UV light. Utilized the designable property of MOFs, we chose aliphatic ligand and pillar ligand to make the 2- dimensional structure with interdigitated structure. By self-assembly of Ni(II) ion and 4-styrylpyridine (spy) and sodium form of adipate,[Ni2(adipate)2(spy)4(H2O)2] successfully synthesized. Contrast with other research, we chose adipic acid, which is an aliphatic ligand, to form a 2-dimensional layer sheet, so we could observe the dynamics when MOF changing their structure. In addition, 4-styrylpyridine successfully formed the interdigitated structure with parallel olefin bond, which can be [2+2] photodimerization by UV irradiation. Irradiation of 365 nm of UV light successfully synthesized [Ni2(adipate)2(spy)2(rctt-ppcb)(H2O)2] by cyclodimerization between two parallel olefin bond of interdigitated 4-styrylpyridine, which was monitored in Single-Crystal to Single-Crystal (SCSC) manner. Consequently, the 2-dimensional layer interdigitated structure was converted to a 3- dimensional framework. Moreover, control of irradiation time, we could obtain a partial photodimerization structure, also monitored by SCXRD. In the second part of thesis, we also synthesized core-shell structure of MOFs via post-synthetic approaches. Collaborated with the simulation team, Prof. Jihan Kim at KAIST, proposed MOF on MOF core-shell structure based on their computational algorithm. As the simulation result, UiO-66 which is cubic crystal system with 12-coordination of zirconium metal in closed packed structure with terephthalate organic linkers and MIL-88B which is hexagonal crystal system with built up from the connection of trimers of iron(III) octahedra with shared μ3-O oxygen with same organic linkers of UiO- 66. In details, the {111} plane of UiO-66 and {001} plane of MIL-88B have similar cell parameter to make core-shell structure successfully. Since, UiO-66 has higher chemical and physical stability than MIL-88B, we chose UiO-66 as core MOF. In addition, in the opposite case, MIL-88B is destructed by strong acidity of ZrCl4, which is precursors of UiO-66. Consequently, we use UiO-66 for core and MIL- 88B epitaxially growth on the every {111} planes of UiO-66 made star-shaped morphology of MOF successfully synthesized as a core-shell structure. Then, we expanded core-shell pairs with the isoreticular structure of UiO-66 and MIL-88B. UiO-66 with MIL-88A which is the shorter ligand than MIL-88B and MIL-88C which is the longer ligand than MIL-88B. Also, UiO-67 which is longer ligand than UiO-66 with MIL-88C. Interestingly, UiO-67 with MIL-88A and MIL-88C didn’t bring up the same result with UiO-66 @MIL-88B. This will be discussed related to MOF flexibility. We also expanded cubic/cubic core-shell pair for further generalized with UiO-67@HKUST-1 pairs. The result of each core-shell synthesis was characterized by X-Ray Powder Diffraction (XRPD). The morphology and distribution of atom were defined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive x-ray Spectroscopy (EDS).
Department of Chemistry
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