Synthesis and Characterization of sI Clathrate Hydrates Containing Hydrogen

Previously, large cage occupancy of H₂ has only been confirmed in the structure II (sII) hydrate. Utilizing a hydrate synthesis pathway involving pressurizing preformed structure I (sI) hydrates, we now show H₂ occupancy in both the small and the large cages of sI, as evidenced by powder X-ray diffraction and Raman spectroscopic measurements. The new H₂ environments were determined to be singly and doubly occupied 5¹²6² cages occurring at 4125–4131 and 4143–4149 cm^–1, respectively. This work serves as proof-of-concept that, by altering the conventional hydrate synthesis procedure to incorporate preformed hydrates, it may be possible to promote the occupancy of H₂ or possibly other guests in a desired structure through a “templating” effect by simply changing the initial hydrate structure