Spectroscopic Studies of Small Molecule Adsorption and Oxidation on TiO2-Supported Coinage Metals and Zr6-based Metal-Organic Frameworks

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Virginia Tech


Developing a fundamental understanding of the interactions between catalytic surfaces and adsorbed molecules is imperative to the rational design of new materials for catalytic, sorption and gas separation applications. Experiments that probed the chemistry at the gas-surface interface were employed through the utilization of in situ infrared spectroscopic measurements in high vacuum conditions to allow for detailed and systematic investigations into adsorption and reactive processes. Specifically, the mechanistic details of propene epoxidation on the surface of nanoparticulate Au supported on TiO2 and dimethyl chlorophosphate (DMCP) decomposition on the surface of TiO2 aerogel-supported Cu nanoparticles were investigated. In situ infrared spectroscopy illustrates that TiO2-supported Au nanoparticles exhibit the unprecedented ability to produce the industrially relevant commodity chemical, propene oxide, through the unique adsorption configuration of propene on the surface of Au and a hydroperoxide intermediate (-OOH) in the presence of gaseous hydrogen and oxygen. Whereas, TiO2-supported Cu aerogels oxidize the organophosphate-based simulant, DMCP, into adsorbed CO at ambient environments. Through a variety of spectroscopic methods, each step in these oxidative pathways was investigated, including: adsorption, oxidation and reactivation of the supported-nanoparticle systems to develop full mechanistic pictures. Additionally, the perturbation of vibrational character of the probe molecule, CO, was employed to characterize the intrinsic µ3-hydroxyls and molecular-level defects associated with the metal-organic framework (MOF), UiO-66. The adsorption of CO onto heterogeneous surfaces effectively characterizes surfaces because the C-O bond vibrates differently depending on the nature of the surface site. Therefore, CO adsorption was used within the high vacuum environment to identify atomic-level characteristics that traditional methods of analysis cannot distinguish.



surface chemistry, infrared spectroscopy, heterogeneous catalysis, propene epoxidation, chemical warfare agent decomposition