Towards novel metal-organic frameworks: synthesis, characterisation and self-assembly

Abstract

The synthesis, characterisation and self-assembly of novel metal-organic frameworks was investigated and reported in this thesis with a view for these materials to be used in heterogeneous catalysis after further modification. Three new materials have been synthesised and their properties discussed with all three structures being solved by single crystal X-ray diffraction methods. Three known and five new elaborate, chiral MOF ligands were synthesised in this investigation. The new ligands were a dicarboxylic acid, two tetracarboxylic acids and two dipyridinyl compounds. All the ligands are based on a bi-2-naphthol core unit. The carbon-carbon cross-coupling reactions used in the synthesis of the new ligands were optimised. All of the ligands produced that contained unprotected, free diols were found not to form novel MOFs in an extensive investigation. A wide range of synthetic conditions were employed in attempt to produce novel MOFs. The ligand with protected diols in conjugation with an achiral co-ligand forms a highly interpenetrated novel MOF, with Zn2+ secondary building units. Two other MOF-like coordination polymers were also successfully synthesised and characterised. One completes a void in the well-known series of MOFs containing the Zn4O secondary building unit and simple dicarboxylic acids. The self-assembly of a series of prototypical MOFs was investigated by a novel solution 1H NMR technique. The solution behaviour of the MOF ligands during the MOF synthesis in these systems is discussed. MOFs containing the Zn4O secondary building unit appear to show fluctuations in ligand concentration, indicating the formation of crystallite species during the first few hours of the synthesis. Some insights are gained about the crystallisation mechanism of the pillared MOFs that were investigated. A dual decrease in the concentrations of both the dicarboxylate and pillaring ligands during the reaction is observed.

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ORCID for Philip A. Gale: orcid.org/0000-0001-9751-4910

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