Thermochemical Interconnectivities of Active Sites on Metal Oxides and their Catalytic Consequences in C−O Formation and C−H Scission Chemistry
type: CreativeWork
description: Surfaces of transition metal oxides consist of metal cations (Mn+) and oxygen anions (O2−), each with distinct catalytic functions—the coordinated protons on lattice O-atoms act as Brønsted acid sites (H+), the coordinatively unsaturated cationic metal centers function as Lewis acid sites (Mδ+−Oδ−), and the anionic lattice O-atoms serve as redox sites (O*). These active sites coexist and collectively catalyze both parallel and sequential reactions during the upgrading of light alkanols and alkanes into value-added chemicals, yet their intrinsic thermochemical and electronic interconnectivities, along with the resulting kinetic correlations of reactions that they catalyze, have not been quantitatively examined and established. In this thesis, alkanol dehydration (DEH) and oxidative dehydrogenation (ODH), the two primary reaction pathways during alkanol conversions, together with alkane ODH, are utilized as model reactions in combined kinetic assessments, chemical titrations, spectroscopic interrogations, theoretical calculations, and thermochemical analysis, to investigate the thermochemical and electronic interconnectivities between two Brønsted sites, redox and Brønsted sites, redox and Lewis sites, and two redox sites. We establish their interconnectivities using a library of structured and unstructured model catalysts, including Brønsted acidic tungsten-based polyoxometalate acid clusters (POM), Brønsted acidic and redox active molybdenum-based POM clusters, and Lewis acidic and redox active CoyMoOx oxides, where their electronic structures are systematically perturbed by either introducing counter cations (e.g., Na+, K+, Cu2+, Mg2+, or Al3+) into POM clusters, varying the Co-to-Mo atomic ratio (y, 0−1) of CoyMoOx oxides, or adjusting oxygen chemical potentials on their surfaces during catalysis by changing oxidant identity (O2 or CO2). Mechanistically, alkanol DEH, encompassing both intermolecular and intramolecular pathways, occurs via the transfer of a bound p…
abstract: Surfaces of transition metal oxides consist of metal cations (Mn+) and oxygen anions (O2−), each with distinct catalytic functions—the coordinated protons on lattice O-atoms act as Brønsted acid sites (H+), the coordinatively unsaturated cationic metal centers function as Lewis acid sites (Mδ+−Oδ−), and the anionic lattice O-atoms serve as redox sites (O*). These active sites coexist and collectively catalyze both parallel and sequential reactions during the upgrading of light alkanols and alkanes into value-added chemicals, yet their intrinsic thermochemical and electronic interconnectivities, along with the resulting kinetic correlations of reactions that they catalyze, have not been quantitatively examined and established. In this thesis, alkanol dehydration (DEH) and oxidative dehydrogenation (ODH), the two primary reaction pathways during alkanol conversions, together with alkane ODH, are utilized as model reactions in combined kinetic assessments, chemical titrations, spectroscopic interrogations, theoretical calculations, and thermochemical analysis, to investigate the thermochemical and electronic interconnectivities between two Brønsted sites, redox and Brønsted sites, redox and Lewis sites, and two redox sites. We establish their interconnectivities using a library of structured and unstructured model catalysts, including Brønsted acidic tungsten-based polyoxometalate acid clusters (POM), Brønsted acidic and redox active molybdenum-based POM clusters, and Lewis acidic and redox active CoyMoOx oxides, where their electronic structures are systematically perturbed by either introducing counter cations (e.g., Na+, K+, Cu2+, Mg2+, or Al3+) into POM clusters, varying the Co-to-Mo atomic ratio (y, 0−1) of CoyMoOx oxides, or adjusting oxygen chemical potentials on their surfaces during catalysis by changing oxidant identity (O2 or CO2). Mechanistically, alkanol DEH, encompassing both intermolecular and intramolecular pathways, occurs via the transfer of a bound p…
author: Cai, Guangming
date published: 2025-06
date modified: 2026-07-27T21:28:02Z
provider: University of Toronto
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Toronto

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property ID: Handle
value: https://hdl.handle.net/1807/145040