A primary concern with the use of ionic liquids for carbon capture is their high viscosity compared with that of commercial solvents. Ionic liquids which employ chemisorption depend on a chemical reaction between solute and solvent for CO separation. The rate of this reaction is dependent on the diffusivity of CO in the solvent and is thus inversely proportional to viscosity. The self diffusivity of CO in ionic liquids are generally to the order of 10 m/s, approximately an order of magnitude less than similarly performing commercial solvents used on CO capture.  The viscosity of an ionic liquid can vary significantly according to the type of anion and cation, the alkyl chain length, and the amount of water or other impurities in the solvent. Because these solvents can be “designed” and these properties chosen, developing ionic liquids with lowered viscosities is a current topic of research. Supported ionic liquid phases (SILPs) are one proposed solution to this problem.