The solubility of CO, in two inexpensive ionic liquids, tributylmethylammonium methylsulfate [TBMN][MeSO4] and tributylme-thylphosphonium methylsulfate [TBMP][MeSO4], has been studied experimentally. A synthetic method was used to measure bubble-point pressures up to 13 MPa for a temperature range of (313 to 368) K. The solubility of CO, in [TBMP][MeSO4] was slightly higher than in [TBMN][MeSO4], but CO, solubilities in both the ionic liquids were surprisingly higher than in the imidazolium analogue 1-butyl-3-methylimidazolium methylsulfate [bmim][MeSO4]. The relatively high melting points of the used ionic liquids may limit their application in CO, capture processes.