Speeding the search for better carbon capture
23 August 2012
A team of researchers has developed a computer model that can identify the best molecular candidates for removing carbon dioxide, molecular nitrogen and other greenhouse gases from power plant flues.
A computer model that can identify the best molecular candidates for removing carbon dioxide, molecular nitrogen and other greenhouse gases from power plant flues has been developed by researchers with the US Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), the University of California (UC) Berkeley and the University of Minnesota.
The model is the first computational method to provide accurate simulations of the interactions between flue gases and a special variety of the gas-capturing molecular systems known as metal-organic frameworks (MOFs). It should greatly accelerate the search for new low-cost and efficient ways to burn coal without exacerbating global climate change.
Berend Smit, an international authority on molecular simulations who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley where he directs Berkeley’s Energy Frontier Research Center, co-led the development of this computational model with Laura Gagliardi, a chemistry professor at the University of Minnesota.
“We’ve developed a novel computational methodology that yields accurate force fields – parameters describing the potential energy of a molecular system – to correctly predict the adsorption of carbon dioxide and molecular nitrogen by MOFs with open metal sites,” Smit says. “All previous attempts at developing such a methodology failed and most people gave up trying, but our model is applicable to a broad range of systems and can be used to predict properties of open-site MOFs that have not yet been synthesised.”
MOFs are crystalline molecular systems that can serve as storage vessels with a sponge-like capacity for capturing and containing carbon dioxide and other gases. They comprise a metal oxide centre surrounded by organic “linker” molecules to form a highly porous three-dimensional crystal framework. When a solvent molecule is applied during the formation of the MOF and is subsequently removed, the result is an unsaturated 'open' metal site MOF that has an especially strong affinity for carbon dioxide.
“MOFs have an extremely large internal surface area and, compared to other common adsorbents, promise very specific customisation of their chemistry and could dramatically lower parasitic energy costs in coal-burning power plants,” Smit says. “However, there are potentially millions of variations of MOFs and since from a practical standpoint we can only synthesise a very small fraction of these materials, the search for the right ones could take years. Our model saves this time by enabling us to synthesise only those that are most ideal.”