Porous Organic Cage CC3: An Effective Promoter for Methane Hydrate Formation for Natural Gas Storage

Herein, the synergistic effect of combining gas hydrates with a novel prototypical porous organic cage, denoted as CC3 (microporous crystalline structure with diamondoid pores), for methane storage is demonstrated using a high-pressure differential scanning calorimeter. Adding CC3 improved the extent of methane hydrate formation significantly, increasing the water-tohydrate conversion from 4.5 to 87.5%, thus increasing the amount of methane stored relative to the water in the system from 0.42 to 8.1 mmol/g. The presence of CC3 also decreased the induction time consistently to 0.8 +/- 0.1 h, whereas without CC3, hydrates only formed 30% of the time at 5.9 +/- 3.9 h of induction time. This increase in conversion and decrease in induction time is attributed to CC3's large surface area, high methane adsorption, and reversible water uptake. A depression in the hydrate dissociation temperature by as much as 1.6 degrees C suggests hydrate formation occurred in the confined space in CC3, most likely in its void and interstitial spacing. CC3 displayed remarkable stability, recyclability, and enhanced performance in promoting methane hydrate formation to achieve a high capacity for methane storage.