The phase behaviour of carbon dioxide/propargylic alcohols and carbon dioxide/oxetanes mixtures has been investigated using in-situ FTIR microspectrometry that allows us determining the evolution of the concentration of each component in the liquid phase as a function of temperature and pressure. It was at the same time possible to look inside the cell and to visualize the expansion of the liquid phase during the increase of the pressure. The measurements were performed at three different temperatures (40, 70 and 100 degrees C) for pressures ranging between 0.1 and 15 MPa. Propargylic alcohol (PA), 2-methyl-3-butyn-2-ol (MBOL), 3-butyn-l-ol (BOL) and trimethylene oxide (TMO) were selected as these molecules are used in the synthesis of cyclic or polycarbonates by coupling with CO2. Thus, we determined the CO2 sorption and the concentration of the substrate in the liquid phase. Thanks to these measurements, we established the pressure-composition phase diagram for the liquid phase of these substrate/CO2 binary mixtures. (C) 2017 Elsevier B.V. All rights reserved.