(4bh) Integrating Circular Hydrogen and Carbon Economies Via Molecular Design of Hybrid Functional Materials Utilizing Innovative Energy Carriers

The goal of my research program is, using molecular design principles, to develop hybrid functional catalytic materials that integrate hydrogen and carbon economies. The specific topics for my proposed research program will include three distinct but interconnected theme areas: (1) The design of molecular electrocatalytic materials, based on hydrogen atom transfer, that can be used to convert and upcycle waste plastics into sustainable materials; (2) The design of nano-scale functionalized hybrid materials that selectively bind carbonates for carbon capture from the ocean; and (3) The design of dual-functional electro and photocatalytic materials for combined hydrogen production and CO₂ conversion. These research efforts will ultimately provide insights into how we harvest hydrogen and carbon from waste streams and the environment to create new integrated circular hydrogen and carbon economies for our sustainable future.

My postdoctoral work with Prof. Ah-Hyung Alissa Park (Columbia University, Earth and Environmental Engineering and Chemical Engineering, Lenfest Center for Sustainable Energy) has focused on using my expertise in molecular design to create nano-scale hybrid functional materials that selectively separate CO₂ and valuable metals (e.g., critical elements) present in industrial flue gas and electronic waste from their constituent components. For this approach, we have begun to investigate how branched poly(ethyleneimine) – functionalized with affinity ligands containing phosphonates, thiophenes, pyrroles, and hydroxypyridinones – can be used to separate critical elements from electronic waste leachate. We aim to integrate these functionalized polymer ligands as the canopy of magnetic core NOHMs (nanoparticle organic hybrid functional materials) to facilitate the concentration of these critical elements by controlling mobility of magnetic NOHMs through the solution. The magnetic core in NOHMs can also serve as a non-thermal energy collector (e.g., microwave, magnetic field) allowing the chemical reactions to be performed using renewable electricity.

During postdoctoral work with Prof. Jack Norton (Columbia University, Chemistry), I developed reaction pathways that can upgrade a range of organic molecules to pharmaceutically relevant organic products using H• transfer. H• transfer reactions allow us to decarbonize chemical synthesis by storing energy in chemical bonds. I have investigated reaction kinetics and mechanisms with earth-abundant metal catalysts (based on cobalt) that can be regenerated with low pressures of H₂ gas. These catalysts facilitate organic cyclization and cycloisomerization reactions using H• transfer. I also studied how central steric considerations, polar effects, and enthalpic contributions were to hydrogen atom transfer reactions. I found that steric considerations were very important, but there also was a non-trivial electronic impact. This is fundamental when thinking about designing new types of H• transfer reactions and will allow us to develop a transformative approach to carry renewable energy through chemical reactions to produce sustainable chemicals and materials. We are currently developing a similar approach to produce hydrogen peroxide from quinone carriers using H• produced using renewable energy.

My Ph.D. research with Prof. Michael Hopkins (University of Chicago, Chemistry) focused on the molecular design and optimization of two families of molecules useful in electro and photocatalysis. In the first project, I found that a potential intermediate in electrocatalytic water reduction initiated by a molybdenum-oxo compound could be isolated using ligands with increased steric bulk. This unusual molybdenum(III)-oxo complex marks the first structurally characterized terminal monomeric entry for this family, and allowed us to study the potential intermediate in electrocatalytic water reduction. A second thrust in this lab revolved around the molecular design of a novel class of earth-abundant photocatalysts, tungsten-benzylidyne complexes. These molecular photoredox catalysts were designed based on their underlying electronic structure using a combination of experiments and theoretical methods. They were found to possess ground state redox potentials that could be varied over 2V, absorbance energies that varied over 1 eV, and excited-state redox potentials that are more reducing than all conventional photoredox catalysts. Furthermore, these photoredox catalysts can be regenerated with H₂ allowing us to decarbonize the production of a wide variety of pharmaceutically relevant molecules.

These prior research experiences have prepared me to create a long-term research program that is focused on molecular design approaches using renewable energy to capture and catalytically convert complex wastes and unconventional resources into sustainable chemicals and materials.

Teaching Interests.

I believe students learn best when they are able to create links between the fundamental and applied through collaborative examples and group problem solving. While I am passionate about research and mentoring others to creatively think about research, I also enjoy mentoring, teaching, and working with undergraduate students. I have mentored 3 Ph.D. students, 4 undergraduate students, and 1 high school student at Columbia University and the University of Chicago. In working with Prof. Park’s group, I am helping a Ph.D. student with her synthetic skills to broaden her expertise and develop highly selective systems for metal ion complexation. During the 2019 school year, as a Scientist-in-Residence with the New York Public Schools, I led a project with the all-female class that taught high school students about solar energy.

At the University of Chicago, I taught and developed new lab modules for an advanced inorganic techniques class and at Columbia University I will be co-teaching an Engineering Elective Class “Introduction to Carbon Management” at Columbia University with Prof. Park in the fall of 2021. I will lead the section on catalytic conversion of CO₂ to value-added materials. With my chemistry and environmental engineering background, I would be well-suited to teach undergraduate classes in related specifically to kinetics and thermodynamics as well as separations. In addition, I would like to develop an elective class focused on “carbon capture and catalytic conversion.” As an interdisciplinary researcher, I am also interested in teaching classes that bridge the boundaries between engineering and chemical sciences. I also have extensive expertise in a wide array of physical characterization methods (NMR, IR, electronic and transient spectroscopies, and mass spectrometry) that may not be conventionally taught, but are often used, in engineering curricula. With the development of these in-situ measurement techniques and automations, the new technology developments can greatly benefit from knowing these tools in the context of process development and optimization. As an instructor, I am committed to teaching inclusively to provide effective learning experiences to students with diverse backgrounds. I am currently enrolled and am auditing a MOOC on Inclusive Teaching in the Classroom offered through Columbia University to expand my teaching tools and outlook.

Selected Publications:

1. Vibbert, H.B.; Hopkins. M.D. Tungsten-Alkylidyne Photoredox Super Reductants. In Progress.

2. Vibbert, H.B.; Park, A.-H. A. Harvesting, Storing, and Converting Carbon from the Ocean to Create a New Carbon Economy: Challenges and Opportunities. In Progress.

3. Shi, S.; Salahi, F.; Vibbert, H. B.; Rahman, M.; Synder, S.A.; Norton, J. R. Generation of ɑ-Boryl Radicals by H• Transfer and their Use in Cycloisomerizations.

4. Vibbert, H. B.; Neugebauer, H.; Norton, J. R.; Hansen, A.; Bursch, M.; Grimme, S. Hydrogen Atom Transfer Rates from Tp-containing Metal-Hydrides to Trityl Radicals. J. Chem. (Special Issue, in Honor of Robert Morris). 2021, 99, 216-220. DOI: 10.1139/cjc-2020-0392.

5. Chen, J.; Vibbert, H. B.; Yao, C.; Bartholomew, A. K.; Aydt, A. P.; Jockusch, S.; Norton, J. R.; Hammond, M.; Rauch, M. Synthesis, Characterization, and Catalytic Activity of Bimetallic Ti/Cr Complexes. Organometallics 2020, 39, 4592-4598. DOI: 1021/acs.organomet.0c00645.

6. Vibbert, H. B.; Filatov, A. S.; Hopkins, M. D. Synthesis, Structure, and Bonding of d³ Molybdenum-Oxo Compounds. Chem. Int. Ed. 2020, 59, 10581-10586. DOI: 10.1002/anie.202001379and 10.1002/ange.202001379 (German Edition).

7. Lorenc, C.; Vibbert, H. B.; Yao, C.; Norton, J. R.; Rauch, M. H· Transfer-Initiated Synthesis of 𝛾-Lactams: Interpretation of Cycloisomerization and Hydrogenation Ratios. ACS Catal. 2019, 9, 10294-10298. DOI: 1021/acscatal.9b03678.

8. Kuo, J. L.; Gunasekara, T.; Hansen, A.; Vibbert, H. B.; Bohle, F.; Norton, J. R.; Grimme, S.; Quinlivan, P. Thermodynamics of H⁺, H·, and H^– Transfer from [CpV(CO)₃H]^–: Comparisons to the Isoelectronic CpCr(CO)₃ Organometallics 2019, 38, 4319-4328. DOI: 10.1021/acs.organomet.9b00586.

9. Rudshteyn, B. R.; Vibbert, H. B.; May, R.; Wasserman, E.; Warnke, I.; Hopkins, M. D.; Batista, V. S. Thermodynamic and Structural Factors that Influence the Redox Properties of Tungsten-Alkylidyne Complexes. ACS Catal. 2017, 7, 6134-6143, DOI: 1021/acscatal.7b01636.

10. Vibbert, H. B.; Ku, S.; Li, X.; Liu, X.; Ximenes, E. A.; Kreke, T.; Ladisch, M. R.; Deering, A. J.; Gehring, A. G. Accelerating Sample Preparation through Enzyme-Assisted Microfiltration of Salmonella in Chicken Extract. Prog. 2015, 31, 1551-1562, DOI: 10.1002/btpr.2167.

11. Morales-Verdejo, C. A.; Newsom, M. I.; Cohen, B. W.; Vibbert, H. B.; Hopkins, M. D. Dihydrogen Activation by a Tungsten-Alkylidyne Complex: Toward Photoredox Chromophores that Deliver Renewable Reducing Equivalents. Commun. 2013, 49, 10566-10568, DOI: 10.1039/C3CC45606D.

12. Li, X.; Ximenes, E. A.; Amalardjou, M. A. R.; Vibbert, H. B.; Foster, K. F.; Jones, J.; Liu, X.; Bhunia, A. K.; Ladisch, M. R. Rapid Sample Processing for Detection of Food-Borne Pathogens via Cross-Flow Microfiltration. Environ. Microbiol. 2013, 79, 7048-7054, DOI: 10.1128/AEM.02587-13.

13. Bork, M. A.; Vibbert, H. B.; Stewart, D. J.; Fanwick, P. E.; McMillin, D. R. Varying Substituents and Solvents to Maximize the Luminescence from [Ru(trpy)(bpy)CN]⁺Inorg. Chem. 2013, 52, 12553-12560, DOI: 10.1021/ic4016367.