Date of Award

Spring 2024

Project Type

Thesis

Program or Major

Chemistry

Degree Name

Master of Science

First Advisor

Christine Caputo

Second Advisor

Roy Planalp

Third Advisor

Anyin Li

Abstract

Anthropogenic warming of the globe is an issue that has attracted a great deal of attention in recent years. This is mainly due to burning fossil fuels which releases greenhouse gases like carbon dioxide into the atmosphere. Because of our society’s high dependence on this energy source, it’s estimated that over 5 million metric tons of CO2 are released into the atmosphere each year. This makes it clear that we must find a clean and renewable way to generate power. Photocatalysis offers a unique solution to this problem. Photocatalytic systems use light to excite an electron which is then used by a catalyst to reduce protons into hydrogen gas (H2). Herein we present the design of a photocatalytic system for H2 production in which electron transfer from a photosensitizer to a catalyst can be improved by reducing the distance between them. Our systems rely on host/guest chemistry, whereby a macrocyclic host can non-covalently and reversibly bind a guest molecule in its cavity. We hypothesize that this strategy will bring the components close together in space, prevent back electron transfer, and allow for recyclability of exhausted catalysts or photosensitizers. The progress towards assembly of this photocatalytic system is presented herein; first as a homogeneous system and then as a heterogeneous system. We demonstrate successful anchoring of the host molecule carboxylic acid-functionalized pillar[5]arene (CA-P[5]) on the surface of titanium dioxide and characterize the composition of this material using 1H NMR, UV-Vis, FT-IR, and XPS spectroscopies. These methods reveal a maximum surface loading amount of 127 nmol CA-P[5] per mg of TiO2 and that the carboxylic acids bind to the metal oxide surface as a bridging bidentate. This lays the groundwork for the future of this project which will use host/guest interactions to immobilize guest functionalized photosensitizers and catalysts on the semiconductor surface to be used to produce H2.

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