(1) In HBCC, CO 2 is separated from a gas mixture by being incorporated into the molecular structure of a gas hydrate, i.e. a solid inclusion compound where hydrogen-bonded water molecules form a host network that captures guest molecules like CO 2 within polyhedral cages . Due to cage diameters on the order of 1 nm gas hydrates exhibit an exceptional CO 2 storage capacity of up to 9.67 mmol per gram of water , i.e., 1 volume of CO 2 hydrate contains up to 164 standard volumes of CO 2 gas . This capacity surpasses conventional commercial solvents like Selexol, Rectisol, and Purisol by almost an order of magnitude and is comparable or exceeds that of many adsorbents .