Polydimethylsiloxane (PDMS) is a promising hydrophobic, CO2-selective solvent for the absorption of CO2 from a hot or warm water-rich, H-2-rich, postwater gas shift reactor (WGSR) stream in an integrated gasification combined cycle (IGCC) power plant. In this work, there are three hydrophobic silicones that are more thermally stable than PDMS, including an iron-stabilized PDMS (PDMS-Fe), poly(dimethyl-co-methylphenyl)siloxane (PDMMPS), and poly(dimethyl-co-diphenyl)siloxane (PDMDPS). PDMDPS is an extremely poor CO2 solvent, which is undesirable for the proposed separation, and a poor hydrogen solvent, which is a desirable trait. PDMDPS and PDMMPS absorb about the same amount of H-2. Although PDMMPS is a much better CO2 solvent than PDMDPS, PDMMPS is a slightly poorer CO2 solvent than PDMS or PDMS-Fe. PDMS-Fe and PDMS are comparable hydrophobic solvents that exhibit the greatest solvent strength for CO2 however, PDMS-Fe and PDMS absorb slightly more hydrogen than PDMDPS and PDMMPS. If the absorption/regeneration process is designed such that the solvent is exposed to temperatures no greater than 230 degrees C, PDMS is recommended due to its low cost. For higher temperatures, the extremely low solubility of CO2 in PDMDPS precludes its use as a CO2-selective solvent. The ferrosilicone additive in PDMS-Fe is designed to inhibit polymer degradation in an oxidizing environment, but it offers no additional stability in the oxygen-free closed system associated with the IGCC. PDMMPS absorbs less H-2 than PDMS or PDMS-Fe but is a slightly poorer CO2 solvent than PDMS or PDMS-Fe. However, PDMMPS is thermally stable in closed systems to 300 degrees C. Therefore, PDMMPS is recommended for prolonged high temperature use as the precombustion carbon capture absorber solvent at absorption/regeneration temperatures above 230 degrees C. Although these hydrophobic silicones exhibit promising attributes for a warm or hot precombustion carbon capture process, the diminishing CO2 solubility and increasing CO2 solubility that occur with increasing temperature will challenge the economic viability of this proposed CO2-selective absorption process.