RESEARCHERS FIND MORE EFFICIENT CO2 SEPARATION MATERIAL

Tamar Hallerman
GHG Monitor
3/15/13

Researchers at the University of South Florida and King Abdullah University of Science and Technology in Saudi Arabia said this week that they have found a hybrid material that can more efficiently separate and capture CO2 from flue gas compared to other adsorbents currently on the market. In a recent report published in the letters section of the journal Nature, the chemists said they have identified a previously discovered but currently underused material that is ideal for CO2 separation due to its lattice structure and hydrophobic qualities. “We’ve kind of come at this from left field. This was a classic compound that nobody was looking at, and it turns out to have superior properties both in terms of selectivity for CO2 and stability when exposed to water,” co-author Michael Zaworotko of the University of South Florida said in an interview this week.

Organic amines for carbon capture currently available on the market tend to have high energy costs associated with their activation and regeneration, and many have to be replaced quicker because their separation capabilities are eventually corroded by the moisture found in flue gas. As a result, researchers interested in carbon capture are driven to find adsorbents that are more efficient and have lower regeneration costs. While many in the field have been driven to metal organic frameworks, Zaworotko said the material that his team rediscovered—SIFSIX-1-Cu—could be a more ideal for CO2 separation because of its nonorganic components in addition to its organic parts, which form a pillared square lattice structure. “Our material is really a hybrid, and that’s the key to the discovery,” he said. “The inorganic components in our structure do the molecular recognition and the organic portions control the structure. The inorganic also possess some very special recognition properties for CO2.”

Zaworotko said he first encountered the parent components of SIFSIX-1-Cu nearly 20 years ago when completing unrelated research. No one since had tested the material for CO2 separation until 18 months ago, when Zaworotko assigned an undergraduate student to examine the material’s pore size. “We had no idea how good [the CO2 selectivity] would be,” he said. “We found that as you decrease the pore size, you dramatically increase the CO2 binding from very good to the best.” That high selectivity, according to Zaworotko, makes the material more efficient for capture, but what makes SIFSIX-1-Cu even more ideal for CO2 separation is the fact that it is hydrophobic. “All of the other porous materials which have a high affinity for CO2 have even higher affinities for water, which causes problems for real-world applications,” he said. “But our material performs just as well in high humidity as it does in dry conditions.” Zaworotko added that the material could also be ideal for separating methane, nitrogen and hydrogen. From here, Zaworotko said that research partners at King Abdullah University will likely test the material further to see if it is practically relevant and can be realistically scaled up and manufactured.