title: Introduction of new functionalities into metal-organic frameworks
Creators: name: Yazigi, François-Joseph
Publisher: name: University of Glasgow
Year: 2018
Subjects: subject: Metal-organic framework.

description: Metal-Organic Frameworks (MOFs) are multidimensional crystallised porous materials built from inorganic nodes separated by organic linkers. Their permanent porosity and their large surface area has brought a widespread interest to these structures for the last twenty years regarding their potential applications such as gas storage, catalysis, sensing and drug delivery. The predictable topologies of MOFs arising from the isoreticular principle have opened the way to functionalisation through rational design and the study of their structure-property relationships. In keeping with that reasoning, this thesis focuses on the introduction of new functionalities into MOFs through careful design of functionalised linkers, and, the work reported in this thesis can be divided in two different subjects. The first is the synthesis of novel functionalised amide containing dicarboxylic linkers for the synthesis of zirconium MOFs. The second subject describes the utilisation of a new hybrid manganese Anderson polyoxometalate as a new kind of functionalised spacer for the so-called POMOF (Polyoxometalate Metal-Organic Framework) materials. Following a general introduction on MOFs describing these materials in terms of structure, synthesis, properties and functionalisation in Chapter 1, Chapter 2 reports the synthesis of amide containing dicarboxylic linkers possessing intramolecular hydrogen bonds and their introduction into UiO-66 type frameworks through both direct synthesis and Solvent-Assisted Linker Exchange procedures. The presence of pendant nucleophilic groups such as amines and hydroxyl units on the MOFs’ organic struts, as well as amide moieties, have shown to increase the CO2 uptake capabilities of porous structures though favourable interactions between consequently created hydrogen bonds and the substrate. Most of these weak interactions generally take place between catenated frameworks and the synthesis of intramolecular hydrogen bond containing linkers is a path to a more rational and controlled way of introducing this kind of functionalisation into a MOF and therefore a path to a higher control over the MOF properties. The synthesis of MOFs containing these new linkers has, however, proven to be more delicate than expected in the first place, and so the unsuccessful initial direct synthesis attempts have directed the thesis to an alternative synthetic route through Solvent-Assisted Linker Exchange of the linkers of a pre-synthesised MOF with the new linkers. The principle and the results as well as the study of a limited incorporation rate in UiO-66 like frameworks alongside stability issues that arised from the presence of the amide containing linkers are described. Following that study, the treatment of the surface of the borosilicate glassware in which the MOF syntheses take place with a chlorinated organopolysiloxane coating has afforded the direct synthesis of single crystals of the desired zirconium MOFs. The loss of their structural integrity upon solvent loss seem to confirm what was observed in the SALE materials, that the amide linkers bring some instability to the usually very stable zirconium MOFs. Two of the amide containing linkers described in Chapter 2 were designed to have metal coordination pockets though a picolinamide moiety. Metalation of linkers containing coordination pockets in MOFs is one controlled way of creating well-defined catalytic centres. In Chapter 3, the coordination properties of these sparsely described binding units are investigated by the synthesis of molecular coordination complexes with the protected version of the linkers (protected carboxylic acid groups by esters that avoid unwanted complexation) and a range of transition metals. The confirmation of the coordinative properties of the picolinamide units by the synthesis of coordination complexes as single crystals was followed by a study of the geometrical deformation of the organic struts induced by the metalation and their potential structural compatibility with UiO-66 like frameworks. This first study was followed by the post-synthetic metalation of the zirconium MOFs described in Chapter 2. The catalytic properties of a palladium functionalised MOF toward Heck couplings were then investigated, and the scope for utilising these systems as heterogeneous catalysts discussed. Chapter 4 differs from the previous chapters by the nature of the investigated functionalised spacers and the resulting coordination networks. Pyridine-functionalised hybrid manganese Anderson POMs were studied as a new class of pre-functionalised linkers for coordination polymers. To situate the work in a larger perspective toward the interest of that approach, a specific introduction on polyoxometalates is present as the beginning of the chapter. This introduction describes the POMs’ nature, chemistry, properties as well as the previously described approaches with which they have been introduced in porous framework so far. The synthesis of six novel coordination polymers as single-crystals as well as their structural description and characterisations are discussed. Some synthetic guidelines are proposed for directing the self-assembly of coordination polymers of this type in future.