Carbon capture and storage from fossil-based power generation is a critical component of realistic strategies for preventing a further rise in atmospheric CO2 concentrations. However, capturing meaningful amounts of CO2 using current technology could result in a prohibitive rise in the cost of electric power consumed. One strategy to minimize energy consumption and economic penalties is to exploit industrial streams in which CO2 is already at high partial pressures, such as the syngas exiting coal gasifiers at integrated gasification combined cycle (IGCC) power plants. In these high-pressure CO2-containing streams, one well-established approach to removing acid gases (CO2 and H2S) from the syngas stream is the use of physical solvents. The physical solvents used in pre-combustion capture of CO2 from coal-gasified power plants are typically more effective at high pressures than chemical solvents. Physical solvents that have been studied for CO2 absorption include N-methyl-2-pyrrolidone (NMP -Purisol), propylene carbonate (Fluor solvent), methanol (Rectisol), and dimethyl ethers of polyethylene glycol (Selexol). One physical solvent that had been studied earlier, but was then seemingly neglected, is tributyl phosphate (TBP), originally identified in the Estasolvan process. This solvent was used for natural gas purification and while it showed only moderate capacity to absorb CO2, it was an excellent solvent for absorbing H2S and SO2. The inclusion of etheric side chains in the form of poly(ethylene glycol) (PEG) units of varying lengths has been shown to impart favorable gas absorption selectivities for CO2 over CH4 and N2, while maintaining good CO2 solubilities and other physical properties for imidazolium ionic liquids by Previously we reported on this approach as being successful for a novel liquid solvent, PEG-Siloxane-1, which is a hybrid solvent of PEG and poly(dimethyl siloxane) (PDMS), and in other recent work. This approach has greatly improved the CO2 absorption capacity and CO2/H2 selectivity of these solvents and therefore was of interest to impart similar properties to TBP.