Organic clathrate compounds, particularly those formed between hydroquinone (HQ) and gases, are supramolecular entities recently highlighted as promising alternatives for applications such as gas storage and separation processes. This study provides new insights into CO 2 −HQ clathrate, which is a key structure in some of the proposed future applications of these compounds. We present a novel synthesis and purification of CO 2 −HQ clathrate monocrystals. Clathrate crystals obtained from a single synthesis and native HQ are characterized and compared using Raman/Fourier transform infrared/NMR spectroscopies, optical microscopy, and thermogravimetric analysis coupled to mass spectrometry. The molecular structure of the clathrate has been resolved by X-ray diffraction analysis, and detailed crystallographic information is presented for the first time.

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Hydroquinone (HQ) forms organic clathrates in the presence of various gas molecules in specific thermodynamic conditions. For some systems, clathrate phase equilibrium and occupancy data are very scarce or inexistent in literature to date. This work presents experimental results obtained for the CO 2 −HQ, CH 4 −HQ, and N 2 − HQ clathrates, in an extended range of temperature from about 288 to 354 K. Formation/dissociation pressures, and occupancies at the equilibrium clathrate forming conditions, were determined for these systems. Experiments showing the influence of the crystallization solvent, and the effect of the gas pressure on HQ solubility, were also presented and discussed. A good agreement is obtained between our experimental results and the already published experimental and modeling data. Our results show a clear dependency of the clathrate occupancy with temperature. The equilibrium curves obtained for CO 2 −HQ and CH 4 −HQ clathrates were found to be very close to each other. The results presented in this study, obtained in a relatively large temperature range, are new and important to the field of organic clathrates with potential impact on gas separation, energy storage, and transport.