There is great interest in methods that can reduce the amount of CO₂ in the atmosphere, e.g., carbon capture and storage (CSS). Metal–organic frameworks (MOFs) and zeolites are typically used for this task. However, alternative materials that sequester CO₂ have also been investigated.

Previously, Janis Louie and co-workers, University of Utah, USA, reported that N-heterocyclic carbene (1) can react reversibly in solution with CO₂ to give a zwitterion [1]. Obtaining sorption isotherm data on (1) has proven difficult as the zwitterion is relatively insoluble in solvents with low vapor pressures.

This issue prompted William Schneider, Joan Brennecke, and Brandon Ashfeld, University of Notre Dame, IN, USA, to examine chemisorption properties of (1) as a free-flowing powder with CO₂ to investigate N-heterocyclic carbenes as neutral reagents for carbon capture [2]. The group used single crystal X-ray diffraction to examine the structure of (1) before and after CO₂ uptake. The group hypothesize that the rapid uptake of CO₂ is associated with a facile reorganization of the structure of (1), thus allowing CO₂ to enter the solid framework between the layers.

The researchers say their findings will have direct implications on further design strategies for CCS reagents, whether for pre- or post-combustion flue-gas separation from coal or natural-gas-fired fuel power plants.

1. A Systematic Investigation of Factors Influencing the Decarboxylation of Imidazolium Carboxylates,
   B. R. Van Ausdall, J. L. Glass, K. M. Wiggins, A. M. Aarif, J. Louie,
   J. Org. Chem. 2009, 74, 7935–7942.
   DOI: 10.1021/jo901791k
2. Solid State Covalent Capture of CO₂ Using N-Heterocyclic Carbenes,
   Monika Vogt, Joshua E. Bennett, Yong Huang, Chao Wu, William F. Schneider, Joan F. Brennecke, Brandon L. Ashfeld,
   Chem. Eur. J. 2013, 19, 11134–11138.
   DOI: 10.1002/chem.201302013