Sorption behavior of CO2 in a low molar mass liquid crystal (MLC) which exhibits a smectic mesophase has been measured by using an electromicrobalance. The sorption values at the same gas pressure are demonstrated to increase significantly at crystalline-smectic and smectic-isotropic transitions. The phase diagram of the MLC-CO2 binary system has been measured through the use of the sorption method. The sorbed CO2 has been shown to influence the phase behavior of the MLC. The isotropization transition of the MLC is found to be broadened by the formation of a biphasic region, which consists of a smectic and isotropic phases. The method for the determination of the compositions of the smectic and isotropic phases within the biphasic region has been offered.