Scientists from ExxonMobil, University of California, Berkeley and Lawrence Berkeley National Laboratory have developed a new material that could capture more than 90% of CO₂ emitted from industrial sources using low-temperature steam, requiring less energy for the overall carbon capture process.

Laboratory tests indicate the patent-pending materials—tetraamine-functionalized metal organic frameworks—capture carbon dioxide emissions up to six times more effectively than conventional amine-based carbon capture technology. Using less energy to capture and remove carbon, the material has the potential to reduce the cost of the technology and eventually support commercial applications.

This graphic shows the interior of a MOF based on the metal magnesium (green balls), and has added molecules—tetraamines (blue & gray)—added to the pores to more efficiently absorb carbon dioxide from power plant emissions. (UC Berkeley graphic by Eugene Kim)

Power plants strip CO₂ from flue emissions today by bubbling flue gases through organic amines in water, which bind and extract the carbon dioxide. The liquid is then heated to 120-150 ˚C (250-300 ˚F) to release the CO₂ gas, after which the liquids are reused. The entire process consumes about 30% of the power generated. Sequestering the captured CO₂ underground costs an additional, though small, fraction of that.

Six years ago, senior researcher Jeffrey Long, UC Berkeley professor of chemistry and of chemical and biomolecular engineering and senior faculty scientist at Berkeley Lab, and his group in UC Berkeley’s Center for Gas Separations, which is funded by the US Department of Energy, discovered a chemically modified MOF that readily captures CO₂ from concentrated power plant flue emissions, potentially reducing the capture cost by half.

They added diamine molecules to a magnesium-based MOF to catalyze the formation of polymer chains of CO₂ that could then be purged by flushing with a humid stream of carbon dioxide.

For CO₂ capture, steam stripping—where you use direct contact with steam to take off the CO₂—has been a sort of holy grail for the field. It is rightly seen as the cheapest way to do it. These materials, at least from the experiments we have done so far, look very promising.

—Jeffrey Long

By manipulating the structure of the metal organic framework material, the team of scientists and students demonstrated the ability to condense a surface area the size of a football field, into just one gram of mass—about the same as a paperclip—that acts as a sponge for CO2. Results of the research were published in Science.

ExxonMobil’s team, led by senior research associate Simon Weston, along with UC Berkeley’s Long and his team of faculty and students have been working collaboratively for eight years to develop this potential carbon capture solution that demonstrates stability in the presence of water vapor, without oxidation, allowing carbon dioxide to be captured from various sources, under a number of conditions.

Additional research and development will be needed to progress this technology to a larger scale pilot and ultimately to industrial scale.

The research successfully demonstrated that these hybrid porous metal-organic materials are highly selective and could capture more than 90% of the CO₂ emitted from industrial sources. The materials have much greater capacity for capturing carbon dioxide and can be regenerated for repeated use by using low-temperature steam, requiring less energy for the overall carbon capture process.

The work was funded by ExxonMobil, which is working with both the Berkeley group and Long’s start-up, Mosaic Materials Inc., to develop, scale up and test processes for stripping CO₂ from emissions.

Resources

• Eugene J. Kim, Rebecca L. Siegelman, Henry Z. H. Jiang, Alexander C. Forse, Jung-Hoon Lee, Jeffrey D. Martell, Phillip J. Milner, Joseph M. Falkowski, Jeffrey B. Neaton, Jeffrey A. Reimer, Simon C. Weston, Jeffrey R. Long (2020) “Cooperative carbon capture and steam regeneration with tetraamine-appended metal–organic frameworks” Science doi: 10.1126/science.abb3976