Abstract
The use of mixed donor and multitopic linkers has been gaining in popularity among the metal-organic frameworkâs (MOFs) field for their ability to form new SBUs and create non-default topologies in MOF structures. This work investigated the design and synthesis of such a ligand, and subsequently, the synthesis of two new metal organic nanotubes (MONTs), and five new MOFs from the utilisation of this ligand. The potential for these systems to be used as functional materials was also examined, with the two MONTs both shown to act as gas storage vessels, and photoactive catalysts.
A general overview of the field was provided in Chapter 1. The history of the field was discussed as well as key terminology that needs to be considered. This is then followed by the key features of MOFs that must be considered, and how the use of both a mixed donor and multitopic linkers can affect the final structural outcome. Finally, the key functionalities of MOFs are discussed, with the main focus on their use for gas uptake, and their involvement in the removal of dyes from industrial wastewater systems.
The utilisation of phenanthroline in MOFs was discussed in Chapter 2, with the discussion primarily focused on the phenanthroline moiety being used as the base of an organic ligand. Thus, the Dubus-Radziszewski mechanism was discussed as an effective method of functionalising the phenanthroline, being able to act as a click reaction to attach a second binding site. Following this, the design of a new mixed donor ligand able to act as a tritopic linker for MOF synthesis was discussed. The synthesis of such a linker (H2L1) was then described, with a consideration of the alternative, more efficient synthetic routes that could be used to achieved H2L1, along with the efficiency of each method. Finally, a second linker (H2L2) was discussed, in which an extra Lewis base in the form of a pyridine nitrogen was added to the H2L1 ligand.
Chapter 3 describes the incorporation of H2L1 into two, isomorphous zinc and cadmium metal-organic nanotubes (MONTs). These structures showed unique 1D to 3D, six-fold interpenetration while still displaying high porosity within the material. The thermal stability of the material was then examined through VT-SCXRD and VT-PXRD, while the chemical stability of the material in a range of solvents was also examined through PXRD.
Following this, Chapter 4 details the viability of the two MONTs to be used as functional materials. Both MONTs showed the ability to uptake gas, with the cadmium isomorph (referred to as Cd.L1) showing to have the highest peak adsorption of both H2 and CO2 out of all MONTs in the literature. Additionally, both materials showed the ability to act as photoactive catalysts for the degradation of inorganic dyes, being able to decompose methylene blue, methyl red and methyl orange within 3 hours.
Chapter 5 details the ability of H2L1 to form complexes with a range of metal ions, namely Cu(II), Mg(II), Ca(II) and Gd(III). Cu.L1 was isolated as two polymorphs, with both showing square channels running down the c-axis of the framework. Mg.L1 formed a structure which was porous down the a-axis, while Ca.L1 showed to be a chiral structure with unique triangular pores running through the c-axis. Finally, Gd.L1 revealed a structure which again contained square 1D pores running down the c-axis of the framework.