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Start date: 2020Subject: search.filters.subject.340601 Catalysis and mechanisms of reactions

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    Asymmetric catalysis via spatially separated chiral and catalytic motifs in multicomponent metal-organic frameworks : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatū, New Zealand
    (Massey University, 2025-11-18) Petters, Ludwig
    Modern life without catalysis is inconceivable. Asymmetric catalysts are a special type of catalyst that preferentially produce one of two possible enantiomers over the other. The ability to selectively obtain exclusively one of the possible enantiomers is of highest importance for modern synthetic chemistry. To enable the transfer of chiral information from the catalyst to the reaction substrates, asymmetric catalysts must be chiral. In conventional asymmetric catalysts, the catalytic and chiral motifs are held close together within one single molecule. In this work, we break the design limitation of conventional asymmetric catalysts with a strategy we call ‘remote asymmetric induction’ (RAI). In RAI catalysts, the catalytic and chiral motifs are independent of each other in their design and synthesis. To achieve this, we use the multicomponent metal-organic framework MUF-77 (MUF = Massey University Framework). MUF-77 consists of three chemically distinct linkers that each occupy a specific position in the framework without disorder or randomness. To create RAI catalysts, the catalytic and chiral motifs are individually anchored to the different building blocks of MUF-77. By virtue of the MUF-77 structure, the catalytic and chiral motifs are in close proximity to one another in a catalytic pore, which creates an active site. This enables the transfer of chiral information to the reaction participants. Initially the reaction scope of the RAI catalyst was expanded by screening a variety of RAI-MOFs incorporating different catalytic and chiral functionalities across a range of model reactions. A promising catalyst for one model reaction was identified and investigated in depth. Through systematic modification of important reaction variables, the variation in enantioselectivity of this system was explored. After parameter optimisation, very good to excellent enantioselectivity was achieved. Control experiments confirmed that the origin of enantioselectivity arises from remote cooperative interactions between the functionalities in the active site. The catalysts were then tested for classical performance metrics and a hypothetical transition state within the MOF pore was proposed. This work establishes RAI as an alternative platform to develop high-performing asymmetric catalysts.
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    Multicomponent metal-organic frameworks : tailoring platforms for transition metal- and bioelectrocatalysis : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatū, New Zealand
    (Massey University, 2025) Auer, Bernhard Stephan
    MUF-77 (MUF = Massey University Framework) is a quaternary, multicomponent metal-organic framework (MOF), constructed from three topologically distinct carboxylate linkers and Zn4O secondary building units. Multicomponent MOFs such as MUF-77, constructed from a set of ligands with different geometries, provide a valuable platform for obtaining ordered and programmable pore environments. In this context, they show great potential as recyclable and stable, heterogeneous catalysts. In this work, we looked at the typical MUF 77 synthesis conditions and investigated the formation of additional crystalline phases. Several new MOFs were discovered, including new multicomponent MOFs. We then investigated MUF-77 for the incorporation of transition metal catalysts. The work included ligand and MOF syntheses and synthetic modifications of the frameworks upon MOF formation. We also embedded a Au(III) catalyst within the MUF 77 framework and evaluated its catalytic properties upon installation into the framework. Finally, we shifted our focus to systems comprising MOF and enzyme components for their electrochemical application in layer-by-layer-grafted electrodes. The work extended our library of potential heterogeneous catalysts, showcasing the great potential of multicomponent systems.
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    Catalysts derived from metal-organic frameworks : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatu, New Zealand
    (Massey University, 2021) Bandara, W. R. L. Nisansala
    The synthesis of atomic-scale catalysts is a blooming field, and these replace the conventional nanocatalysts due to their high atom utilization, selectivity, and unique catalytic activity. Metal-organic frameworks (MOFs) serve as promising precursors for the synthesis of single-atom catalysts (SACs). This study focused on the synthesis of SACs on nitrogen-doped hollow carbon by using MOFs and MOF composites followed by pyrolysis. The synthesis of two SACs namely rhodium SACs (Rh SACs) and cobalt SACs (Co SACs) by different methods, their characterization, and catalysis was explored. Rh SAC synthesized in this work hydrogenates nitroarenes with high consumption and high selectivity. Moreover, Co SAC did little or no hydrogenation of the nitroarenes. Further applications of these SACs were explored by employing them in oxygen reduction reaction (ORR), NO abatement, and Fenton-like catalysis. Moreover, the synthesis of two types of hollow nanoboxes (HNB) namely HNB-1 and HNB-2; using MOFs and MOF composites, their characterization and applications were also investigated. HNB-1 was used to make electrode supercapacitors and it showed comparable activity to activated carbon. Further attempts were made to use HNB-2 as a fluorescence sensor. Finally, several ideas on synthesising SACs and HNBs were proposed as a part of future work.
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    New routes to planar chiral ligands and their use in asymmetric catalysis : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatū, New Zealand
    (Massey University, 2021) Mungalpara, Maulik
    This thesis contains 8 chapters detailing 3 optimised methods to synthesise [2.2]paracyclophane derivatives and our studies in the C-H activation field, namely selective remote β-C-H activation of cyclic amines, and enantioselective γ-C(sp³)-H functionalisation of cyclic amines, as well as a future direction. As the main focus of this thesis is on the development of novel planar chiral [2.2]paracyclophane derivatives, Chapter 1 starts with a brief description of [2.2]paracyclophane chemistry. A short introduction about the synthesis of key enantioenriched [2.2]paracyclophane derivatives is given. Finally, a short introduction of the recent applications of [2.2]paracyclophane-based ligands in asymmetric catalysis is also mentioned. Chapter 2 describes the synthesis of (RSp,SRP)-4-tert-butyl[2.2]paracyclophane phosphine oxide (SPO) and attempts to synthesise its asymmetric variant. Further, its synthetic utility is investigated, mainly in Suzuki-Miyaura cross-coupling, Buchwald-Hartwig amination, and Au(I)-catalysed cyclisation reactions. Additionally, a general route to the P-stereogenic [2.2]paracyclophane-derived phosphines via the reduction of tertiary phosphine oxides is reported. Chapter 3 mainly outlines attempts for β-C(sp³)-H activation of cyclic amine to target the shortest route of epibatidine moiety. A stepwise approach is mentioned. Firstly, a range of heteroatom-substituted secondary phosphine oxides (HASPOs) is evaluated to access (chiral) indolines via intramolecular C(sp³)-H activation. Next, an intramolecular C(sp³)-H activation of 7-azanorbornane, a core skeleton of epibatidine, is investigated. The third approach is mainly targeted for the directing-group-assisted intermolecular C(sp³)-H activation of 7-azanorbornane. Lastly, enantioselective γ-C(sp³)-H activation of N-cyclohexylpicolinamide using various chiral Brønsted acids, again targeting the epibatidine moiety by the late-stage cyclisation, is described. In a search for suitable planar chiral Brønsted acid, an optimised single-step protocol for the synthesis of [2.2]paracyclophanes carboxylic acid derivatives is reported in Chapter 4. This protocol proceeds via C(sp²)-H activation of chiral oxazolines and their coupling with bromo[2.2]paracyclophanes. Chapters 5 & 6 are related to pyridine sulfinates. Chapter 5 describes an attempted regioselective C-H functionalisation of aromatic acids via desulfitative coupling with pyridine-2-sulfinate. A detailed study with catalytic Pd(OAc)₂ and pre-formed palladacycle is mentioned. The effect of catalytic Pd(OAc)₂ on homo-coupling of pyridine-2-sulfinates is also investigated. The potential of sulfinates as nucleophilic coupling partners is investigated in Chapter 6. A novel methodology to synthesise pyridyl[2.2]paracyclophanes is described. The method involves desulfitative cross-coupling reactions between pyridine sulfinates and bromo[2.2]paracyclophanes. One of the interesting results of the desulfitative coupling with the unreactive (±)-4-bromo-5-amino[2.2]paracyclophane is also mentioned. Chapter 7 explains the future scope of the research work mentioned in this thesis. Finally, Chapter 8 describes the experimental procedures and characterisation of the synthesised compounds mentioned in Chapters 2 to 6.
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    Catalysis of thermo-catalytic methane decomposition : a thesis presented for the degree of Master of Science in Nanoscience at Massey University, Palmerston North, New Zealand
    (Massey University, 2020) Powick, Samuel Thomas
    The use of hydrogen gas as an energy carrier is a proposed pathway to eliminating greenhouse gas emissions from fossil fuels. However, emissions-free production of hydrogen is more costly than traditional high-emissions hydrogen production processes such as Steam Methane Reformation (SMR). To address this, a process called Thermo-catalytic Methane Decomposition (TCMD) is being commercially developed. This process uses methane (natural gas) to produce hydrogen gas and high quality solid carbon which can be sold to offset the price of the hydrogen produced. TCMD has the potential to be cost-competitive with SMR. A key feedstock in the TCMD process is a low cost catalyst, because the carbon produced deposits on the catalyst and deactivates it. The most commercially viable choice of catalyst has been identified as iron ore, or hematite, due to its high activity and lifetime, and its low cost [13, 23]. The TCMD process could have applications in New Zealand to supply the heavy transport market, but for this to happen, a domestic source of iron ore is required for use as a catalyst. New Zealand’s primary source of iron ore is in the form of titanomagnetite found in ironsands, which has different properties to hematite. As a result, this research was commissioned to evaluate the effectiveness of New Zealand ironsands as a catalyst for TCMD. The effects of temperature, flow rate, catalyst composition, and aggregate particle size on ironsand catalytic activity, lifetime, and carbon by-product quality are evaluated relative to a hematite control.