<p>A clathrate hydrate is a crystalline composed of water molecules forming cage-like structures that encapsulate gas molecules. There are three types of crystallographic structures: I, II, and H. Structure of the hydrate formed with pure CO₂ is structure I (sI). These structures exhibit high gas storage capacity and large enthalpy changes during formation and dissociation, making them useful for energy storage and gas separation technologies. This study investigates the encapsulation of ethanol molecules in CO₂ hydrates formed from aqueous ethanol solutions with varying ethanol mass fractions (0.10 and 0.40). Hydrate solid samples were analyzed using powder X-ray diffraction (PXRD). The lattice constant of CO₂ hydrate formed from a 0.40 ethanol mass fraction aqueous solution in this study was 11.902&#xa0;Å at 123&#xa0;K. This value exceeds both the lattice constant of simple CO₂ structure I hydrate reported by Makiya et al. for hydrate formed from a ethanol mass fraction aqueous solution. The increase in the mass fraction of ethanol corresponds to an increase in the fugacity of ethanol in the system. It is inferred that the measured lattice expansion is relevant to an increased occupancy of ethanol in the large cages of the sI hydrate, which correlates with the increasing mass fraction of ethanol. This is because the increase in the mass fraction of ethanol corresponds to an increase in the fugacity of ethanol in the system.</p>