(3v) Computational Engineering of Catalysts Beyond the Active Site

Sustainable chemical transformations of conventional and emergent feedstocks to fuels and fine chemicals require significant technological advancement to develop new catalysts that have high intrinsic reactivity, stability, and selectivity. One avenue to tackle these grand challenges in catalyst design is to optimize the secondary environments around active sites by varying the pore size of zeolites or metal-organic frameworks (MOFs) to tune their shape-selective properties. Hydrophobic or hydrophilic defects can also be introduced to tune the local solvation environment around active sites. Simultaneously considering catalyst active site identity, pore environment, and solvent interactions is a considerable challenge, due in part to the interconnectedness of these features: e.g., the active site metal, pore size, and proximity of defects all affect the solvent structure. Computational modeling is central in the effort to elucidate how these design criteria intersect and further advance the development of new catalysts to address the current and future environmental challenges we face.

In my graduate research with Prof. Jeffrey Greeley I investigated how the identity of metal sites, pore size, and defects affect the shape and stability of solvents and transition states in zeolite catalysts. I used quantum chemistry techniques to show that hydrophobic/hydrophilic defects in zeolite Beta affect the structure of water networks and therefore mediate the local solvent environment around active sites [1]. These models were directly applied to show how confined solvents restructure dehydration transition states [2], interrogating how solvents and micropores control reaction kinetics. Through microkinetic modeling, I derived kinetic expressions to show that metal active sites restructure during dehydration, and the zeolite framework has a non-innocent role on kinetics [3]. Furthermore, the thermodynamic stability of this restructuring is directly related to the active metal atom identity [4], providing a glimpse at the complexities in each of these catalyst properties. Close collaborations with Prof. Rajamani Gounder’s group enabled these theories to relate to experimental observations.

While my graduate work focused on intrinsic kinetics in microporous catalysts, my postdoctoral work with Prof. Randall Snurr included computational modeling of how mass transfer and diffusion in MOF catalysts are affected by pore size, shape, and connectivity. For polar molecules, the spatial distribution of metal-oxide nodes in the MOF have a dominant role in controlling diffusion, which in turn, can impact reaction kinetics, especially at high conversion or low temperature. Taken together, I have developed the tools necessary to investigate how the identity of active sites and pore shape affect intrinsic reaction kinetics as well as intracrystalline mass transfer rates. In my independent research group, I will formally combine quantum chemical calculations of catalyst active sites and their surrounding environments with molecular simulations of solvent structures and diffusion to extend computational predictions of catalyst activity, stability, and selectivity to realistic materials of interest for thermal and electrocatalysis applications at realistic catalyst operating conditions.

Selected Publications

1. C. Bukowski, J.S. Bates, R. Gounder, J. Greeley, “Defect-Mediated Ordering of Condensed Water Structures in Microporous Zeolites,” Angewandte Chemie International Edition 58 (46), 16422-16426, 2019.
2. S. Bates^† and B.C. Bukowski^†, J.P Greeley, R. Gounder, “Structure and Solvation of Confined Water and Water-Ethanol Clusters within Microporous Brønsted Acids and their Effects on Ethanol Dehydration Catalysis,” Chemical Science, in press. ^†denotes equal contribution from both authors.
3. C. Bukowski, J.S. Bates, R. Gounder, J. Greeley, “First Principles, Microkinetic, and Experimental Analysis of Lewis Acid Site Speciation During Ethanol Dehydration on Sn-Beta Zeolites,” Journal of Catalysis 365, 261-276, 2018.
4. C. Bukowski, J. Greeley, “Scaling relationships for molecular adsorption and dissociation in Lewis acid zeolites,” The Journal of Physical Chemistry C 120 (12), 6714-6722, 2016.

Teaching Interests

The dissemination of technical knowledge, as well as critical thinking, rationalism, inclusion, environmental stewardship, and compassion is necessary to cultivate new generations of technical leaders, policymakers, and future educators. My experiences as a teaching assistant for a senior level process control course and second year thermodynamics course were influential in developing the organization skills for classroom instruction as well as experience in fostering curiosity from the students. I was fortunate to have opportunities to write and present lectures for these courses, where I could begin to find my personal teaching style and iterate how I presented material with each lecture experience. From my work in the process controls course, I received the 2016 Undergraduate Award for Teaching Excellence in a Senior Course which is awarded by the undergraduate student body. I elected to take a course in Educational Methods in Engineering by Prof. Philip Wankat to learn in detail how to design a course curriculum, fairly evaluate students, and promote a culture of diversity and inclusion in engineering. I was also introduced to many of the current teaching methodologies and received evaluations on my lectures by Prof. Wankat. I have continued to develop my teaching skills by providing guest lectures in graduate elective classes taught by Prof. Greeley, Prof. Gounder, and Prof. Snurr. These experiences have instilled a strong desire to teach the engineering principles in an environment that respects and fosters diverse backgrounds and experiences.

I would like to better integrate new developments in computer simulation and data science in chemical engineering for undergraduates. These cutting-edge techniques provide a competitive edge for students that pursue industry positions and graduate degrees, and I would like to offer an advanced undergraduate / graduate elective course in these topics. My teaching expertise includes undergraduate and graduate level thermodynamics, kinetics and reaction engineering, separations and mass transport, and engineering mathematics.