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Hydrothermal synthesis, structure and properties of lanthanide polybenzoates and related polymers

Authors Choi, Chun Lung
Issue Date 2011
Summary Metal-organic frameworks (MOFs) are an important class of organic-inorganic hybrid materials that have emerged over the past twenty years. They have great commercial importance in particular to the fields of selective sorption and separation of gases, catalysis and luminescence. Chapter 1 surveys the background to the successful design and preparation of MOF solids, as well as lanthanide based luminescence. Chapter 2 describes the synthesis and characterization of biphenyl based carboxylic acids and an exploration of their coordinative chemistry from hydrothermal crystallization, with a view to open stable MOF preparation. The main approach is to carry out Miyaura-Suzuki coupling. The metal coordination polymers formed from five biphenic acids with a variety of transition metals and lanthanides under hydrothermal and solvothermal conditions were then explored and about 20 new phase types are reported. Further exploration of MOF materials generated from biphenate type ligands is continued in Chapter 3. In this the addition of neutral N-donors such as 4,4’-bipyridine as co-ligands to form open frameworks such as [M2(3,3-BPA)2(4,4-bipy)] is explored. Finally, Chapter 4 focuses on the photoluminescence from mixed-lanthanide coordination polymers.. A methodology for semi-quantitative photoluminescence (PL) measurements of powdered samples was developed. Both cascade energy transfer mechanism and reduction of self-quenching can play important roles in the enhancement of PL. Aromatic polymers showed much stronger PL than aliphatic analogues. In (Eu0.1:Tb99.9)2(2,2-biphenate)3(H2O)2 the Eu emission is comparable to the Eu homo-polymer, whilst the original Tb emission is reduced by ca. 80%. Such effects involving energy transfer between Ln centers appeared greater for polymers with direct O bridges between Ln centers and shorter Ln---Ln separations of less than 4.5Å . Some of our findings have implications for the preparation of efficient and highly active PL thin-films based on lanthanide carboxylate polymers.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2011
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