With the growing concern about global warming caused by CO2 emissions, there is an immediate and urgent need for efficient CO2 capture and reuse.
About 80% of the CO2 added to the air annually is removed through either dissolution in the oceans or absorption by living organisms. Since water dissolution is slow and indiscriminate, researchers are studying how natural systems trap CO2 and how it might be separated from a mixture of gases. Nature uses membranes for separating molecules, and enzymes to catalyze CO2 absorption in water. By translating the molecular designs of biological membranes, and incorporating enzymes, biomimetic membranes can be developed.
A team of researchers from Sandia National Laboratories and the University of New Mexico (UNM) have worked together since 2004 on biomimetic membranes. Their joint efforts led to a 2011 R&D 100 award-winning membrane for water purification that improves access to clean water. That membrane mimicked the nanoscale pore design of cellular membranes that filter water in the human body.
The Sandia-UNM team’s latest success applies biomimetic membranes to CO2 capture. UNM Assistant Research Professor Ying-Bing Jiang is fabricating membranes in his lab based on a nanoporous platform developed by Jeff Brinker, a Sandia Fellow and Distinguished and Regent’s Professor of UNM. Modeling work done by Sandia Distinguished Member of Technical Staff and UNM Adjunct Professor Susan Rempe guides membrane design.
Biomimetic membrane technology depends on advanced synthetic strategies, including molecular self-assembly of nanoporous membranes and atomic layer deposition to tailor pore geometries and interior surfaces. Theoretical studies reveal how nanopores stabilize water solutions and how biological enzymes in those solutions speed up CO2 dissolution. Those insights are important to optimize pore design and enzyme function for commercial applications.
The current biomimetic membranes trap water droplets within the nanopore structures. Each water droplet contains enzymes that specifically convert CO2 into bicarbonate, a charged molecule that is highly soluble and moves rapidly across the water layer. On the other side of the membrane, the enzyme carries out the reverse reaction, converting bicarbonate back to CO2. Thus, the liquid-layered membrane permits highly efficient CO2 absorption from power plant flue gas and produces pure CO2 gas for reuse in oil recovery.
Compared to conventional CO2 absorption methods, biomimetic membranes provide a simple, compact, and more energy-efficient approach. Biomimetic membranes also separate CO2 from mixtures of gases faster and with higher selectivity than other membranes.
Future applications for the Sandia-UNM team’s work might include embedding multiple types of enzymes that convert CO2 to fuel, or tuning the membranes to transport ions for efficient power generation from seawater. The potential for biomimetic membranes to help clean up our air and water or lower the cost of power generation will continue to be developed by the Sandia-UNM collaborative partnership.