| Abstract |
During the last decade, MOFs (Metal-Organic Frameworks) have attracted remarkable attention worldwide, because of their great potential as functional porous solids in the field of gas storage/separation and catalysis. MOFs belong to a new class of crystalline nanoporous materials that have good thermal stability, high void volume, uniform pore size and shape. They are made of metal oxide vertices interconnected by rigid organic molecules, through self-assembly processes. As MOF chemistry expands, there is a demand for more complex structures with increased functionality, that allow the combination of porosity with novel framework properties. This goal could be achieved through the utilization of suitable functionalized ligands or with post-synthetic methodologies.
In the first part of the present Ph.D. Thesis we have synthesized the sulfur analogue of the terephthalate dianion, namely the tetrathioterephthalate dianion. This ligand has never been used before in the synthesis of coordination polymers. Herein, we report the first crystalline, semiconducting coordination polymers based on zinc, manganese and cadmium.
In the second part of the Thesis, we have synthesized the sulfone and hydroxyl derivatives of the 4,4’-biphenyl-dicarboxylic acid for the development of new MOFs. We note that these ligands have never been used before in the entire family of coordination polymers. We have discovered a novel family of sulfone functionalized MOFs based on first row transition metals as well as lanthanides. Accordingly, 23 new MOFs have been isolated and structurally characterized, from which 13 are three-dimensional. Many of these 3D MOFs, consist of novel secondary building units (SBU), both organic and inorganic. Gas sorption measurements including N2, Ar, H2, CO2 and CH4 revealed accessible porosity in some of these MOFs with enhanced H2 enthalpy of adsorption and CO2/CH4 selectivity.
In the case of lanthanides MOFs, we discovered a remarkable single-crystal-to-single-crystal transformation, at room temperature. Novel, 3D isostructural solids were obtained in the case of La, Ce, Pr.
Finally, the reaction between the ligand 2-hydroxyl-4,4΄-biphenyl dicarboxylic acid with zinc nitrate afforded a new 3D open-framework solid, made of two interpenetrating cubic sub-lattices. Each sub-lattice consists of the well known [Zn4O]+ SBU in the IRMOF series, however, the network accommodates also the ligand 4,4-biphenyl dicarboxylate. After removing the gust solvent molecules from the as-synthesized material, nitrogen adsorption isotherm recorded at 77 K, revealed the presence of permanent porosity and a specific surface area of ~1300 m2g-1.
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Σύνθεση, χαρακτηρισμός και ιδιότητες νέων πορωδών πολυμερών συναρμογής
