Browsing by Subject "coordination polymer"
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Item Pendant Functional Groups in Metal-Organic Frameworks - Effects on Crystal Structure, Stability, and Gas Sorption Properties(2013-03-14) Makal, Trevor ArnoldThe primary goal of this research concerns the synthesis and characterization of metal-organic frameworks (MOFs) grafted with pendant alkyl substituents to enhance stability and gas sorption properties for use in clean-energy related technologies. Initially, the focus of this work was on the synthesis and comparison of two isostructural MOFs built upon octahedral secondary building blocks; one with no alkyl substituents, and its dimethyl-substituted counterpart. The dimethyl-substituents are observed to enhance the stability of the framework, resulting in high Langmuir surface area (4859 m2 g-1) and hydrogen uptake capacity at 77 K and 1 bar (2.6 wt%). In the second section, the length of pendant alkoxy substituents in semi-flexible MOFs was evaluated through the synthesis and characterization of two isostructural MOFs, one with dimethoxy (PCN-38) and one with diethoxy pendant groups (PCN-39). While PCN-38 exhibited moderate surface area and hydrogen uptake capacities, PCN-39 underwent structural change upon activation leading to a redistribution of pore sizes and selective adsorption of hydrogen over larger gases. This structural transformation is believed to originate from optimal space filling of the pendant groups. In the third section, a series of NbO-type MOFs were synthesized with dimethoxy, diethoxy, dipropoxy, and dihexyloxy substituents and the relationship between chain length and framework stability identified. Increasing chain length was observed to increase moisture stability of the MOFs, resulting in a superhydrophobic material in the case of the dihexyloxy derivative. Thermal stability, however, decreased with increasing chain length, as evidenced from in situ synchrotron powder X-ray diffraction measurements (PXRD). This is in contrast to data obtained from thermogravimetric analysis and shows that the standard use of thermogravimetric analysis, which measures combustion temperatures, may not always provide an accurate description of the thermal stability of MOFs. The role of pendant groups in gas adsorption processes was evaluated through identification of side chains and guest species in the pores of MOFs through in situ synchrotron PXRD measurements. In summary, three separate isostructural series of MOFs with various pendant groups have been discussed in this dissertation, with the roles of those pendant groups toward crystal structure, stability, and gas sorption properties analyzed.Item Synthesis, Structure and Characterization Of Polynuclear Rare Earth Alkoxide Clusters(2014-04-30) Dempsey, Scotty LeeThe versatile polyol/polyamine supporting ligand TDCI (1,3,5-tris(dimethylamino)- 1,3,5-trideoxy-cis-inositol was synthesized, and several lanthanide complex clusters of this ligand were produced.The coordination chemistry and characterization of these triangular lanthanide alkoxide clusters was explored. Molecular products include Ln?(H??TDCI)?(L) (Ln = Y, Eu, Gd, Tb, Dy, Ho, Er; L =MeOH, H?O, dipivaloylmethanide, acetylacetonate, dibenzoylmethanide, tetraacetylethane, hexafluoroacetylacetonate).The dysprosium and gadolinium analogues of these clusters were used as secondary building units and were incorporated as preformed entities into coordination polymers linked by squarate (C?O?)?? and benzenedicarboxylate. The dysprosium clusters Dy?(H??TDCI)?(MeOH)? and Dy?(H??TDCI)?(dpm)? (dpm = dipivaloylmethanide) as well as the coordation polymer Dy?(H??TDCI)?(C?O?)?/? were shown to exhibit slow relaxation of magnetization characteristic of single-molecule magnet behavior. The europium and terbium analogues were characterized by spectrofluorimetry. Hexanuclear oxo-centered Dy and Gd clusters were synthesized: the OH-face capped Gd?(??-O)(??-OH)?(??-O)?(PhB(OEt)?)?(dpm)?(HOEt)? and Gd?(??-O)(??-OH)?(dpm)? as well as the edg-bridged [Dy?(??-O)(??-OCH?CF?)??(OCH?CF?)?][Na(thf)?]?. All compounds were characterized by single-crystal X-Ray diffraction.