Abstract
In recent years, pillared MOFs have grown in interest. The pillaring of MOFs has been found to have a remarkable influence on the surface area, size and shape of the pores in MOFs. In the attempts of making pillared Lanthanide MOFs, six bi-ligand MOFs were produced. One lithium structure was also produced during the study.
In chapter 1, MOF chemistry, isoreticulation and the role of pillaring are introduced. Some significant light weight and lanthanide MOF structures are reviewed from the literature. The design of the bridging ligands that are used in this project is also discussed.
In chapter 2, more detailed information of the ligand synthesis and the description and comparison of the MOFs that were characterised are provided.
Two ligands, 4'-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-[1,1'-biphenyl]-3-carboxylic acid (L1H) and 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzoic acid (L2H) were synthesised to be used as bridging ligands in MOF chemistry. Two pillaring ligands terephthalic acid (H2bdc) and [1,1'-biphenyl]-4,4'-dicarboxylic acid (H2bpdc) were also used in the MOF studies. Six lanthanide MOFs were isolated and characterised by single crystal X-ray diffraction. Five of the six lanthanide MOFs were 3D networks.
Nd-MOF 352, [Nd(bdc)(L1)].4DMA, presented a 3D pillared framework. The framework consisted of a double-walled arrangement and pseudo-paddlewheel arrangement. There were two types of channels in the framework. One being a sinusoidal channel while the other was a flattened oval channel. The calculated void space when all solvent molecules were removed is 58.3%.
Nd-MOF 421 and Gd-MOF 424, [M(bdc)(L2)]2.5DMA (M = Nd or Gd), are isomorphous. They both presented a 3D pillared framework, and both consisted of a pseudo-paddlewheel arrangement. There were sinusoidal channels within the framework. The calculated void space when all solvent molecules were removed is 43.6%.
Gd-MOF 482, [Gd2(bpdc)2(L1)2].9DMA.0.25H2O,was a two-fold interpenetrating pillared MOF. A double-walled arrangement and pseudo-paddlewheel arrangement were observed within the interpenetrated frameworks. The two interpenetrated frameworks were found to be the same. The calculated void space of a single framework when all solvent molecules were removed is 49.9%.
Nd-MOF 502, [Nd2(bpdc)(L1)2(DMA)4]X2.10DMA (X = unknown anion, possibly OH-), was a 2D dual-ligand system. A pseudo-paddlewheel arrangement and double-walled arrangement were observed in the framework. The bound DMA solvent molecules on the metal ions prevented the formation of a 3D framework. The calculated void space when all solvent molecules were removed is 41.0%.
Gd-MOF 527, [Gd4(bpdc)5(bdc)(DMA)4].2DMA,was formed during an investigation of the formation of diamond-shaped crystals which were found in numerous reaction tubes. The structure contained both pillaring ligands, bdc and bpdc and no bridging ligand, L1. The structure was 3D and has two different types of channels, square channels and diamond-shaped channels. The calculated void space when all solvent molecules were removed is 58.3%.
In addition, Li-MOF 375, [Li(L1)(L1H)],was formed when attempting to grow lightweight MOFs with L1H ligand. The resulting crystalline material was determined to be a centrosymmetric dimer. This dimer forms a 2D H-bonded structure.
In Chapter 3 the experimental details are provided, and appendix contains details of Crystallographic Tables and NMR spectra.