Insights into the Crystal Structure and Clathration Selectivity of Organic Clathrates Formed with Hydroquinone and (CO₂ + CH₄) Gas Mixtures

Abstract

Organic clathrates, particularly those formed by hydroquinone (HQ) and gas mixtures, have been far less studied than other inclusion compounds, such as gas hydrates. In this study, experiments and molecular dynamics simulations were performed on mixed (CO 2 + CH 4)−HQ clathrates. Single crystals were synthesized using gas mixtures with different compositions, ranging from pure CO 2 to pure CH 4. The crystal structure, the guest occupancy in the clathrates, and the variation of the crystal lattice parameters according to clathrate composition were obtained by X-ray diffraction measurements. In addition, molecular dynamics simulations were performed on the same systems, with state-of-the-art molecular models and force fields. The experimental results obtained and the molecular dynamics simulation estimations were in good agreement. The clathration selectivity was also calculated on the basis of experimental results, and the composition of the solid phase was correlated with the composition of the gas phase at equilibrium. These new insights into these structures will be useful from both a fundamental and a practical point of view, particularly for further developing innovative gas separation techniques using HQ clathrates.

Novel Hydroquinone-Alumina Composites Stabilizing a Guest-Free Clathrate Structure: Applications in Gas Processing

“…in Mak and Lam (2004), 34 and a = b = 16.60(1) Å and c = 5.52(1) Å in Han et al (2012) 36 ). These lattice parameter values confirm that the guest-free clathrate structure formed in this composite may be of type I, with no (or only slight) lattice distortion of the cavity, 37 in perfect line with our conclusions from NMR measurements. Actually, one of the most interesting features revealed by this XRD analysis is that the guest-free clathrate structure formed during the impregnation process is very stable, as it is still present in the particles more than 2 years after their synthesis.…”

Accurate crystal structures and chemical properties from NoSpherA2

“…46,47,81,82 Many studies focus on carbon dioxide inside the hydroquinone voids for fuel and energy science, but the occupancy (or lling ratio) of the voids is unclear. 46,47,80,82 In the example of the HQ-CO 2 compound shown here, the occupancy of the entity in the void was rened in HAR to be precisely 0.854(2) (Fig. 4(a)).…”

“…80 Various guest molecules can be trapped and then be transported through the host structure, which leads to various applications of hydroquinone clathrates. 46,47,81,82 Many studies focus on carbon dioxide inside the hydroquinone voids for fuel and energy science, but the occupancy (or filling ratio) of the voids is unclear. 46,47,81,83 In the example of the HQ-CO2 compound shown here, the occupancy of the entity in the void was refined in HAR to be precisely 0.854(2) (Figure 4 (a)).…”

“…We have chosen the CO 2 -hydroquinone clathrate as an example of how the guest-molecule position and partial occupation can be rened accurately in HAR. 46,47 Conformational disorder. In biological macromolecular crystallography, disorder is omnipresent in the main molecules as well as in the solvation sphere.…”

Extremely Slow Diffusion of Argon Atoms in Clathrate Cages: Implications for Gas Storage in Solid Materials

“…From the simulations, the mean square displacement (MSD) of Ar atoms was obtained to evaluate the diffusive behavior of Ar. The force field used to describe HQ has been presented in the previous works, ,, where its ability to represent quantitatively the crystal lattice parameters of the empty HQ clathrate has been demonstrated.…”