하이드로퀴논 포접 화합물의 압력 변화에 따른 구조 변이에 관한 연구

Abstract

Organic clathrates is one of the potential host materials for gas storage, as they often form stable inclusion compounds with a variety of guest species over a wide range of temperature and pressure conditions. It has been reported that organic clathrates are more stable than clathrate hydrates over a wide range of temperature and pressure conditions. In this work, hydroquinone(HQ) is selected as a possible organic material to be used for storing and transporting gas. HQ clathrate is known to have ability of capturing various molecules while changing its crystal structure from α-form to the β-form at high pressures. The guest-free, CO2-loaded, CH4-loaded, N2-loaded, and CH3OH-loaded HQ clathrates were synthesized by gas-phase reaction and recrystallization process. The pressure-driven structural transformation of clathrate compounds was observed by a diamond anvil cell and Raman spectroscopy up to pressures of 10 GPa. The CO2-, CH4-, N2- and CH3OH-loaded HQ clathrates transformed into the crystalline α-form HQ at ~5GPa, and recovered to their original β-form HQ clathrates at ambient condition upon returing pressure. In contrast, the guest-free HQ clathrate remained the α-form HQ upon decreasing pressure to ambient condition after its structural transition to the α-form HQ at ~0.25GPa, indicating that the pressure-induced structural transition of the guest-free HQ clathrate is completely irreversible. This result provides a useful guide to determine the stability of structural integrity of organic clathrate compounds.