A biphasic ionic liquid and compressed carbon dioxide system has a number of advantages for efficient homogeneous catalysis. For reactions that were limited by mass transfer, the presence of CO₂ increased the apparent reaction rate. However, in well agitated systems and at constant moles of 1-octene, adding the pressure of CO₂ reduced the apparent reaction rate. Detailed phase equilibrium studies were conducted to determine volume expansion of the IL phase with CCO₂ and the phase behavior and mixture critical points between the reactants/product and CO₂ that ultimately affect the concentration of the reactant. With an appropriate understanding of kinetics, mass transfer and phase equilibria these biphasic IL/CO₂ reaction systems can properly be understood and engineered. This presentation will illustrate the inclusive effect of CO₂ on Rh-catalyzed hydrogenation and hydroformylation of 1-octene in a biphasic ionic liquid/CO₂ system.