Catalytic Oxidations with Lignin-Based Ligands

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The Catalysis Program of the Chemistry Division of the National Science Foundation supports the research program of Professor Mahdi Abu-Omar of the University of California, Santa Barbara. This project is focused on the area of sustainability or "Green Chemistry". The project seeks new ways to produce industrially important chemicals and fuels. This work is relevant to the economy of United States, the largest producer of chemical products globally. Chemical producers seek renewable starting materials. They also seek to use abundant resources when possible. Safety in a chemical process is a third consideration. These goals motivate research on chemical reactions that are environmentally friendly. Professor Abu-Omar's project uses cheap and abundant elements such as manganese and iron along with plant-based groups to form the new catalysts that in turn, speed up the desired reactions. Detailed analyses of the rates of these chemical reactions give insights into how the catalyst works on an atomic level. In support of the broader impacts of the project, Dr. Abu-Omar is actively engaged in an outreach program involving community college (CC) students, who are largely from underrepresented groups, in laboratory research. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Mahdi Abu-Omar of the University of California, Santa Barbara (UCSB) is designing and synthesizing catalysts based on first row transition metals, specifically manganese and iron. These catalysts are further designed using lignin-based ligands (LBL). The synthesis of LBL is high yielding, atom economical, and satisfies many of the Principles of Green Chemistry. The design of LBL provides a motif that is highly suited for coordination chemistry but yet resistant to oxidative degradation. Iron- and manganese-LBL complexes are then employed to generate chlorine dioxide on-demand from chlorite in aqueous solution under ambient temperature and at neutral pH. A significant improvement in chlorine dioxide production is to avoid oxygen atom transfer (OAT) from the catalyst to chlorite to make chlorate, which is a persistent pollutant. Under investigation is the oxidation of phenanthrene and phenols (aromatic compounds) by in situ generated chlorine dioxide. In a unique approach, two catalytic cycles are coupled in tandem to achieve oxidations with dioxygen as the stoichiometric oxidant.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.