Oxidation Chemistries Over Catalysts Containing M-N4 Active Sites

Rational design of catalysts can result in formulations with performance that exceed those developed through empirical trial-and-error approaches. However, in for metal-containing porous catalysts, the development of active site structure-function relationships are convoluted by heterogeneities in metal binding site structures. One strategy to overcome these limitations is to encapsulate a metal-containing molecular complex within a porous host. Metal phthalocyanine complexes are promising due to their thermal stability and similar binding sites to biological oxygenase enzymes and metal nitrogen-doped carbons. These complexes can be housed within the supercages of faujasite zeolites (MPC@FAU), creating a hybrid catalyst. This dissertation comprises an integrated synthesis, structure, and function study of MPC@FAU catalysts compared to more heterogeneous metal-nitrogen doped carbons (M-N-C). CoF16PC@FAU reacted distinctly from Co-N-C in gas phase CO oxidation with O2, as CoF16PC@FAU deactivated rapidly with time on stream while Co-N-C was more stable. Apparent kinetics measured over Co-N-C were consistent with previous reports. The cause of deactivation over MPC@FAU samples was determined to be the strong adsorption of reactants, but which reactant was responsible was dependent on the metal center in each complex. Density functional theory (DFT) suggests that O2-activation takes place over MPC, after which the first CO2 is formed through a Langmuir-Hinshelwood (L-H) step and the second is formed through an Eley-Rideal (E-R) step, and is a distinct reaction mechanism from N-doped carbons. In liquid phase cyclohexane oxidation, apparent kinetics were similar between FeCl16PC/FAU and Fe-N-C. Data for both samples regress well to a radical mediated E-R mechanism. Apparent kinetics were also similar for FeCl16PC/FAU and Fe-N-C for gas phase propane hydroxylation. Kinetic data regressed well to an E-R mechanism for both FeCl16PC/FAU and Fe-N-C, and these catalysts had similar trends in predicted coverages of surface intermediates and calculated degrees of rate control based on regressed rate constants. Overall, these results support the choice of MPC hybrid materials as representative models for more heterogeneous M-N-Cs, and demonstrate their reactivity in a series of liquid and vapor-phase reactions with multiple oxidants.

Grantor dc:publisher

University of Alabama Libraries

Year dc:date.issued

2026

Author dc:creator

• Iaia, Ethan P.

Advisor dc:contributor.advisor

• Harris, James W.

Contributors dc:contributor

• Bakker, Martin G.
• Sheehan, James D.
• Szilvasi, Tibor
• Turner, C. Heath

• catalysis
• doped carbon
• kinetics
• molecular complexes
• oxidation
• zeolite

Statement dc:rights

• All rights reserved by the author unless otherwise indicated.

Language dc:language.iso

en_US, English

Dc Identifier Other

1233326

OAI identifier oai:identifier

oai:ir.ua.edu:123456789/18047