Date of Award
8-2024
Document Type
Campus Access Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry/Inorganic Chemistry
First Advisor
Jonathan Rochford
Second Advisor
Jason Evans
Third Advisor
Michelle Foster, Mary Pryce
Abstract
Efforts to mitigate environmental changes are at the forefront of research advancements with the target of urging society toward a carbon neutral fuel economy. Sequestering atmospheric carbon dioxide (CO2) and reducing it to useful fuels (e.g. formic acid, HCO2H) or petrochemical precursors (e.g. carbon monoxide, CO) is a major focus in this regard, though the electrocatalytic conversion of CO2 is a critical challenge. Homogeneous transition metal complexes are prime candidates for the development of selective CO2 reduction catalysts as they offer easy access to a diverse range of metal oxidation states and ligand structures for fine–tuning of electronic properties. Of particular focus, the [fac–MnI(X)(N^N)(CO)3]n class of pre–catalysts (X = Br–, n = 0; X = CH3CN, n = +1; N^N = polypyridyl ligand) have seen a rapid growth in popularity as CO2 reduction catalysts, in both electrocatalytic and photocatalytic systems, as more sustainable substitutes for their well–established Re congeners. The overarching theme of this dissertation is to improve upon the mechanistic understanding of product selectivity by enhancing our knowledge of the variables that influence competing reaction pathways such as second coordination sphere (SCS) effects of the catalyst, electrolyte acidity, and electrolyte composition. Pairing of SCS and acid source effects will allow for the investigation of CPET mediated metal–hydride (M–H) generation in CO2 to HCO2– conversion. Chapter 1 provides the reader with an overview of Mn(I) metal complexes for CO2 reduction by discussing previous literature as well as the catalytic mechanism observed for Mn(I) polypyridyl catalysts. Chapter 2 studies the influence of including a bridging N-H group in the bipyridine ring of a Mn(I) catalyst. In Chapter 3, ligands are functionalized with amino groups of varying substitution to study structure-activity relationships in [fac–MnICH3CN(R2bpy)(CO)3]+ pre-catalysts to form each desired product in the presence of varied acid sources. Following suit, Chapter 4 studies ligands functionalized with H-bond donor groups to once again understand the relationship of pre-catalyst and acid source to products formed. Finally, in Chapter 5, CPET mediators are incorporated in CO2 electrocatalysis with previously studied catalysts to observe if mediated HAT may influence product selectivity.
Recommended Citation
Murphy, Alana, "PH Dependent Product Selectivity of Manganese(I) Polypyridyl-Based Electrocatalysts for CO2 Reduction" (2024). Graduate Doctoral Dissertations. 980.
https://scholarworks.umb.edu/doctoral_dissertations/980
Comments
Free and open access to this Campus Access Thesis is made available to the UMass Boston community by ScholarWorks at UMass Boston. Those not on campus and those without a UMass Boston campus username and password may gain access to this thesis through resources like Proquest Dissertations & Theses Global (https://www.proquest.com/) or through Interlibrary Loan. If you have a UMass Boston campus username and password and would like to download this work from off-campus, click on the "Off-Campus UMass Boston Users