Technology

Lead PI:

• Doug Stephan, University of Toronto

Project Investigator:

• Eugenia Kumacheva, University of Toronto

Post-Doctoral Fellows:

• Roman Dobrovetsky, University of Toronto
• Jesse Greener, University of Laval
• Kun Liu, University of Toronto
• Dinesh Jagadeesan, University of Toronto
• Tongen Wang, University of Toronto

Graduate Students:

• Milad Abolhasani, University of Toronto
• Rachelle Choueiri, University of Toronto
• Tayseer Mahdi, Universit of Toronto
• Gabriel Menard, University of Toronto
• Dan Voicu, University of Toronto

Goal

This research will evaluate the use of frustrated Lewis pairs (FLP) in the activation, capture and utilization of CO₂ using a three-phase approach:

1. Exploration and development of the range of FLP systems capable of sequestering CO₂.
2. Design, synthesis and demonstration of FLP systems for catalytic reduction of CO₂.
3. Optimization of the molecular units required for construction of such catalysts to maximize the catalyst efficacy and potential for application in commercial processes.

Activities

Having established that CO₂ can be captured with FLPs derived from phosphines and boranes, initial efforts will probe the range of Lewis acids and bases that effect similar binding.

Numerous combinations are proposed, including nitrogen (amine), aluminum, and transition metal systems.

The most promising and reactive systems will be used to develop catalytic reactions such as reduction to methanol and conversion to CO and water or to CO and oxide products. Structural modifications to the Lewis acid and base will maximize catalyst activity. Additional exploitation of FLP chemistry with, for example, silanes could open new paths to homogeneous catalytic CO₂ reduction and even the formation of novel polymers.

Critical needs in this new FLP study are the reaction mechanisms and kinetic data, which provide the basis for development of a catalytic system for CO₂ reduction. Reactions between CO₂ and FLPs are rapid and thus difficult to study by conventional methods. The research team has demonstrated that the progress of the reaction of amines and CO₂ can be followed by monitoring the size of gas bubbles in a microfluidic channel, offering a new approach to the acquisition of kinetic data gas/liquid reactions with minimal use of reagents and solvents.

Key Developments

The project has progressed from a proven CO₂ capture system and demonstration of stoichiometric conversion to the successful catalytic reduction of CO₂ to CO. Of the FLP candidates tested so far, zinc-based compounds show high reactivity, however the formation of an undesirable byproduct requires further investigation. In parallel and utilizing one reaction system for consistency, capabilities of the microfluidic cell system have advanced to include:

• An algorithm to digitize the visual imaging of flow and bubble size along the flow cell,
• IR species detection to validate the kinetic data, and
• Heating of the cell to collect thermodynamic data at various temperatures.

Publications

STEPHAN

R.Dobrovetsky, D.W. Stephan, Stoichiometric Metal-Free Reduction of CO using Syn-Gas J. Am. Chem. Soc. 2013, 135, 4974–4977. DOI: 10.1021/ja401492s

G. Ménard, D.W. Stephan, CO₂ Reduction via Aluminum Complexes of Ammonia Boranes Dalton Trans. 2013, 42, 5447-5453 .DOI: 10.1039/C3DT00098B.

MJ.Sgro, D.W. Stephan Activation of CO₂ by Phosphinoamide Hafnium Complexes Chem. Commun. 49, 2610-2612 DOI:10.1039/C3CC38286A (cover invited).

R.Dobrovetsky, D.W. Stephan, Catalytic Reduction of CO₂ to CO Using Zn(II) and In situ Generated Carbodiphosphorane as a Frustrated Lewis Pairs Angew. Chem.Int. Ed. 2013, 52,:2516-2519. doi: 10.1002/anie.201208817

M.J. Sgro, J.Dömer, D.W. Stephan, Stoichiometric CO₂ Reductions using a Bis-Borane-based Frustrated Lewis Pair, Chem. Commun. 48, 7253-7255.

L.J. Hounjet, C.B. Caputo, D.W. Stephan, Phosphorus as a Lewis Acid: CO₂ Sequestration with Amidophosphoranes, Angew. Chem. Int. Ed. 51, 4714–4717.

R.C. Neu, G. Ménard, D.W. Stephan, Exchange Chemistry of tBu₃P(CO₂)B(C₆F₅)₂Cl, Dalton Trans , 41, 9016- 9018

G. Ménard, D.W. Stephan, Stoichiometric Reduction of CO₂ to CO by Al-Based Frustrated Lewis Pairs, Angew. Chem. Int. Ed 50, 8396–8399.

I.Peuser, R.C.Neu,X. Zhao, M.Ulrich, B.Schirmer, G.Kehr, R.Fröhlich, S.Grimme,G.Erker, D.W.Stephan, CO₂ and Formate Complexes of Phosphine-Borane Frustrated Lewis Pairs, Chem. Eur. J. 17, 9640–9650.

X.Zhao, D.W. Stephan, Bis-Boranes in the Frustrated Lewis Pair Activation of Carbon Dioxide, Chem. Commun. 1833-1835.

R.C. Neu, E. Otten, A. Lough, D. W. Stephan, The Synthesis and Exchange Chemistry of Frustrated Lewis Pair-Nitrous Oxide Complexes, Chem. Sci. 2, 170-176.

M.A. Dureen, D.W. Stephan, Reactions of Boron Amidinates with CO₂ and CO and Other Small Molecules, J. Am. Chem. Soc. 132, 13559–13568.

KUMACHEVA

Abolhasani, M.; Singh, M.; Kumacheva, E.; G?nther, A. Cruise Control for Segmented Flow. Lab Chip 12, 4787-4795 (2012).

Abolhasani, M.; Singh, M.; Kumacheva, E.; G?nther, A. Automated Microfluidic Platform for Studies of Carbon Dioxide Dissolution and Solubility in Physical Solvents. Lab Chip 12, 1611-1618 (2012).

Li, W.; Liu, K.; Simms, R.; Greener, J.; Jagadeesan, D.; Pinto, S.; Guenther, A.; Kumacheva, E.* Microfluidic Study of Fast Gas-Liquid Reactions. J. Am. Chem. Soc. 134, 3127-3132 (2012).