RUI: Production of Highly Reactive Metal-Oxo Species with Molecular Oxygen and Visible Light for the Selective Oxidative Catalysis

Western Kentucky University Research Foundation, Bowling Green KY

Investigators

Abstract

The reaction of organic compounds with the oxygen in air with a catalyst is one of most important processes conducted daily on a large scale for the production of valuable chemicals, remediation of pollutants, and the production of energy. In this project, Dr. Rui Zhang and his students at Western Kentucky University (WKU) are designing efficient catalysts that can use sunlight to activate the atmospheric oxygen and transfer it to inexpensive materials for production of high-value commodity chemicals. The use of solar energy and atmospheric oxygen rather than a chemical reagent in oxidation of bulk chemicals is more sustainable, generates less chemical waste, and potentially reduces economic costs. This research impacts the fundamental science and technology of green chemistry. The project is providing cutting-edge research experiences for the participating undergraduate students in science, technology, engineering and mathematics (STEM) disciplines and thereby training future STEM professionals. High school students from the Gatton Academy, the residential Math and Science Academy located on WKU's campus, are also spending time in the laboratory and learning about catalysis research. With this award through the Chemical Catalysis Program, Dr. Rui Zhang and his students at Western Kentucky University are developing sustainable, "green" and selective oxidation catalysis via high-valent transition metal-oxo species, using molecular oxygen and visible light (sunlight). Prior studies in this area have demonstrated the unique reactivity of a series of oxo bisporphyrins and oxo corroles as useful photocatalysts. They can be used for oxidations in which high-valent transition metal-oxo species are produced through a disproportionation reaction. The salen-based catalysts are accepted as one of the most successful and widely applicable catalytic systems. However, mechanistic studies on these salen systems have so far been hampered by the fact that the catalytically active species appear only as fleeting putative intermediates. Now Prof. Zhang is exploring new ways to produce and elucidate the salen-metal-oxo oxidizing species, a challenging task. A variety of metal-salen complexes that contain photo-absorbing groups are being synthesized and investigated in an effort to capture a broad spectrum of light. The findings from this work are extending the scope of metal-oxo chemistry and exploring reactivity patterns of salen-metal-oxo complexes. More importantly, the synthesis and study of a series of oxo bis-metal-salens with attached light-harvesting units are leading to the new generation of photocatalysts for important aerobic oxidations. In addition, this award enables Dr. Rui Zhang to maintain a strong undergraduate research program, actively engage STEM students in all stages of the research projects. This effectively prepares them as future STEM professionals. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.