CO2 Fixation: Iron Complexes for Catalysis

Alexander J. Kendall – Tyler Lab Group Meeting – 4/16/2014

Why Fix CO2?

• Convenient C1 source • 0.04% Earth’s atmosphere v/v

• Common industrial byproduct• Often excellent quality (>99%

pure)

• Limited uses of CO2

• Super-critical CO2

• Cooling agent

• Industrial pollutant (combustion)• Greenhouse gas

• Move towards carbon neutral processes

Don’t Fix CO2?

• Difficult to isolate out of gas mixtures

• Very thermodynamically stable

• Kinetically fairly inert

• Difficult to use compared to CO as a C1 source

• Carbon neutral process• Low energy input

• Generally requires noble or rare-earth metals

Global Industrial CO2 Stream

• Industrial CO2 emissions = 29 billion metric tons per year

• Less than 1% is reused

• CO2 contributes to rising levels of greenhouse gasses

• 1820 = 280 ppm• 1981 = 340 ppm• 2013 = 395 ppm

• CO2 contributes to ocean acidification

• 35% of all CO2 generated re-dissolves in bodies of water

Emissions, 2.90E+10

Chemical Capture, 1.10E+08

Neat Capture, 1.80E+07

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E+10

1.0E+11

Emissions Chemical Capture Neat Capture

Metr

ic T

ons o

f C

O2

Industrial CO2 Emissions vs Consumption 2010

http://www.noaa.gov/ Beller, M.; Bornscheuer, U. T. Angew.

Chem. Int. Ed. 2014, 53, 2–4.

Two Approaches to CO2

• Carbon(IV) to Carbon(IV)• Thermodynamically favorable

• Energetically neutral or exothermic

• Narrow window of chemically useful compounds

Beller, M.; Bornscheuer, U. T. Angew. Chem. Int. Ed. 2014, 53, 2–4. ; Tolman, W. B. Activation of Small Molecules: Organometallic and Bioinorganic Perspectives; 1 edition.; Wiley-VCH: Weinheim, 2006.

Two Approaches to CO2

• Carbon(IV) reduction (fixation)• Require input energy to reduce carbon(IV)

• Energy intensive processes can generate more CO2 than they fix

• Extensive range of useful compounds (varying degrees of cost/benefit)

• Hydrogen storage

Beller, M.; Bornscheuer, U. T. Angew. Chem. Int. Ed. 2014, 53, 2–4. ; Tolman, W. B. Activation of Small Molecules: Organometallic and Bioinorganic Perspectives; 1 edition.; Wiley-VCH: Weinheim, 2006.

4+ 3+

3+2+ 2+ 0 2- 4-

Thermodynamic Considerations

• ∆𝐻𝑓𝑜 (kJ/mol)

CO2(g)-393.5

CH4(g)-74.4

H2(g)0.0

H2O(g)-241.8

∆Ho= -164 kJ/mol

• Carbon(IV) reduction• Use high energy reagents to become exothermic

• Net systemic energy loss • Hydrogen production (endothermic)

• Generate heat/pressure

• Net CO2 gain

Kinetic Considerations

• Activating CO2

• Non-polar

• Electrophilic

• Generally requires dual activation• Nucleophile to attack C

• Electrophile to attack O

• Requires geometry change

Ansari, M. B.; Park, S.-E. Energy Environ. Sci. 2012, 5, 9419.

Kinetic Considerations

Ansari, M. B.; Park, S.-E. Energy Environ. Sci. 2012, 5, 9419.

HOMO

LUMO

133-135o

The First Isolated Metal-CO2 Complex

Aresta, M.; Nobile, C. F.; Albano, V. G.; Forni, E.; Manassero, M. J. Chem. Soc. Chem. Commun. 1975, 636–637.

The First Fe-CO2 Reduction

Gao, Y.; Holah, D. G.; Hughes, A. N.; Spivak, G. J.; Havighurst, M. D.; Magnuson, V. R.; Polyakov, V. Polyhedron 1997, 16, 2797–

2807.

Early FeII-H Reduction of CO2

Field, L. D.; Lawrenz, E. T.; Shaw, W. J.; Turner, P. Inorg. Chem. 2000, 39, 5632–5638.

FeII-H Disproportionation of CO2

Allen, O. R.; Dalgarno, S. J.; Field, L. D. Organometallics 2008, 27, 3328–3330.

CO2 Reduction to Oxalate at FeI

Lu, C. C.; Saouma, C. T.; Day, M. W.; Peters, J. C. J. Am. Chem. Soc. 2007, 129, 4–5.

CO2 Reduction to Oxalate at FeI

Lu, C. C.; Saouma, C. T.; Day, M. W.; Peters, J. C. J. Am. Chem. Soc. 2007, 129, 4–5.

CO2 Reduction to Oxalate at FeI

Saouma, C. T.; Lu, C. C.; Day, M. W.; Peters, J. C. Chem. Sci. 2013, 4, 4042–4051.

FeI-Mediated CO2 Disproportionation

Sadique, A. R.; Brennessel, W. W.; Holland, P. L. Inorg. Chem. 2008, 47, 784–786.

FeI-Mediated CO2 Disproportionation

Sadique, A. R.; Brennessel, W. W.; Holland, P. L. Inorg. Chem. 2008, 47, 784–786.

CO2 Reduction to SynGas at FeII

Thammavongsy, Z.; Seda, T.; Zakharov, L. N.; Kaminsky, W.; Gilbertson, J. D. Inorg. Chem. 2012, 51, 9168–9170.

Catalytic CO2 Hydrogenation to Formic Acid

Ziebart, C.; Federsel, C.; Anbarasan, P.; Jackstell, R.; Baumann, W.; Spannenberg, A.; Beller, M. J. Am. Chem. Soc. 2012, 134, 20701– 20704.

Catalytic CO2

Hydrogenation to Formic Acid

Ziebart, C.; Federsel, C.; Anbarasan, P.; Jackstell, R.; Baumann, W.; Spannenberg, A.; Beller, M. J. Am. Chem. Soc. 2012, 134, 20701– 20704.

Summary & CO2nclusions

• CO2 is an industrial byproduct that has use as a feedstock chemical

• Requires development of inexpensive CO2

reduction catalysts

• Activating CO2 at Fe requires hydrides (reduction) or disproportionation (CO & CO3

2-)

• Catalytic hydrogenation of CO2 is possible, but requires H2, 60 Atm and is low yielding.

• Better CO2 catalysts are needed to utilize as a general C1 synthetic building block

• Materials & biological CO2 fixation also lacking

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E+10

1.0E+11

Emissions ChemicalCapture

Neat CaptureMetr

ic T

ons o

f C

O2

Industrial CO2 Emissions vs Consumption 2010

Questions