Mon, Dec. 8, 2014, 3:15pm - 5:30pm
Frick Chemistry Laboratory, Taylor Auditorium
Host: Rob Knowles
3:15 p.m. – Public research seminar, Taylor Auditorium
4:30 p.m. – Research proposal, A81
Towards Rational Design of Catalysts for Organic Synthesis and Energy Catalysis
The importance of catalysts in modern science can hardly be overstated. The rational design of tailored molecules and materials as efficient and robust catalysts is a central goal in both organic and inorganic chemistry. Here, two different approaches to catalyst development are presented for asymmetric organic synthesis and energy catalysis.
The first part outlines the mechanism-based design and optimization of organocatalysts for enantioselective organic transformations. A class of thioureas possessing extended aromatic substituents has been demonstrated as a privileged catalyst scaffold for a wide variety of transformations proceeding through ion pair intermediates. Through detailed mechanistic analysis, the catalysts were shown to direct rate acceleration and enantioinduction via transition-state stabilization using a series of attractive, noncovalent interactions. Particularly, anion-binding and cation–π stabilization act in synergy to bind and stabilize the ion-pair transition states of the key bond forming and breaking processes. The mechanistic study led to a new solution to a traditionally challenging synthetic problem, highly enantioselective selenocyclizations.
The second part presents an interdisciplinary molecular-materials approach to the development of robust, efficient and selective catalysts for CO2 reduction. In this approach, homogenous small-molecule catalysts are integrated with stable, porous and tunable covalent organic frameworks (COFs). The resulting new material performs CO2 reduction to CO in neutral aqueous buffer with relatively low overpotential and excellent Faradic efficiency. This COF also exhibits long-term stability and high selectivity for CO production over competing H2 evolution. The structural tunability of COFs allows us to optimize the catalytic activity by synthesizing isoreticular frameworks with extended pore sizes to enhance surface area and diffusion rate.