Hydrogen-bonded clathrate hydrate as tunable media for efficient methane storage

The tuning effect of gas hydrates, which creates additional nanospaces to accommodate gaseous guest while maintaining favorable formation conditions, is recognized as a promising strategy for energy gas (CH4 or H2) storage. Although the tuning behavior has been demonstrated on sI and sII gas hydrates, it has not been studied in sH hydrates which have the largest potential gas storage capacity. Here, we report the sH tuning behavior in 1-Methylpiperidine + CH4 hydrate systems under mild formation conditions (e.g., 263.15 K, and 8.0 MPa). The occurrence of sH tuning behavior is experimentally verified via 13C solid-state NMR with DFT calculations. The tuning patterns are observed below the eutectic composition of water + 1-Methylpiperidine, which strongly suggests that the supercooled aqueous phase existing on the surface of ice particles plays a significant role in the tuning phenomena. We expect these finding can open new strategies for enhancing capacity for gas storage, and provide critical insights into the fundamental nature of clathrate chemistry.