Multi-component metal-organic frameworks

The synthesis of metal-organic frameworks (MOFs) with new structures and multi-functional pore environments is an area of growing research interest. One route to forming materials of this kind is through the synthesis of multi-component MOFs, which may include multiple organic ligand types or metals in the framework. This thesis presents new examples of multi-component MOFs which aim to demonstrate how this approach affects the properties of the resulting frameworks. Chapter 1 details the terminology surrounding metal-organic frameworks and includes a review of the literature. The overall aims of the thesis are presented at the end of this chapter. A series of mixed-ligand MOFs are presented in Chapter 2, combining multiple organic ligands which perform the same structural role within the framework but contain different functionalities. X-ray diffraction studies revealed that the pore size and geometry of the products can be systematically altered through compositional control. Chapter 3 is an investigation into defect formation through the systematic inclusion of a dicarboxylate ligand into frameworks based on tricarboxylate ligands. X-ray diffraction and gas adsorption studies on the mixed-ligand products show them to be isostructural to the single ligand analogues and contain defects which induce porosity into an otherwise non-porous system. The preparation of zinc-based anionic MOFs which contain viologen cations in their pores are detailed in Chapter 4. A reduction of the viologen counter-ions from the dication (yellow) to the radical cation (blue) was observed with heating or irradiation. Stability of the viologen radical cations within the MOFs was investigated through electron paramagnetic spectroscopy and was shown to be dependent on the framework topology. Finally, Chapter 5 describes the synthesis and characterisation of a range of mixed-lanthanide coreshell MOFs, containing gadolinium, terbium and europium. These materials exhibit different emission properties than those of an isostructural framework containing randomly distributed lanthanide centres.