Date of Award

Fall 2024

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

Gonghu Li

Second Advisor

Christopher Bauer

Third Advisor

Margaret Greenslade

Abstract

Utilization of CO2 by photocatalytic reduction to generate energy-rich fuels is a rapidly growing area of interest. Diimine-tricarbonyl Re(I) complexes are well-known CO2-reduction catalysts with excellent selectivity toward CO production. In this thesis, various strategies for coupling molecular Re(I) catalysts with semiconductor surfaces are investigated.In Chapter II, four molecular Re(I) catalysts are evaluated in photocatalysis. The effect of immobilizing these catalysts on TiO2 is studied. These Re(I) catalysts showed excellent activities in photocatalytic CO2 reduction in the presence of Ru(II) photosensitizer giving turnover numbers (TONs) ranging from 368 to 738 in 2 hours. In Chapter III, a Re(I) complex with pyrene moieties is synthesized for surface immobilization on graphitic carbon nitride (g-C3N4) via π-π interactions. However, no enhancement in photocatalysis is observed by coupling with g-C3N4. In Chapter IV, a new strategy is attempted to couple molecular Re(I) complexes with g-C3N4. In this strategy, potential diimine ligands are incorporated into g-C3N4 during the synthesis of g-C3N4 via calcining precursor ligands together with urea. Re(I)-carbonyl moieties are successfully synthesized on the resulting materials by reacting with Re(CO)5Cl. Interestingly, the synthesized Re(I) catalysts show selectivity towards methane production in CO2 reduction, which is rarely reported in photocatalysis using Re(I) complexes in the literature. In Chapter V, the synthesis of g-C3N5 is attempted in order to obtain a new light-harvesting semiconductor for molecular catalysts, although the synthesis was not successful.

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