High SF6/N2 selectivity in a hydrothermally stable zirconium-based metal–organic framework

Porous Organic Cages for Sulfur Hexafluoride Separation

“…The SF 6 isotherms for CC3 α suggested excellent potential for SF 6 separation from nitrogen, and therefore the nitrogen isotherms were measured at equivalent temperatures (Figure S2) to allow the calculation of ideal adsorbed solution theory (IAST) predicted selectivity (Figures and S3). The industrially relevant composition for separation of an SF 6 /N2 mixture is SF 6 :N2 = 10%:90%. , At 1 bar pressure, CC3 α gives a selectivity of 178 at 273 K and 74 at 298 K. This surpasses the most promising candidate material previously reported, UiO-66-Zr (selectivity = 74, at 1 bar, 293 K) and other similar framework materials such as Zn-MOF-74 (selectivity = 46, at 1 bar, 298 K), Ca-A zeolite (28 at 1 bar, 298 K), and zeolite-13X (44 at 1 bar, 298 K) . The total capacity of CC3 α for SF 6 is higher than that of many of the frameworks reported (e.g., UiO-66-Zr is ∼1.5 mmol, at 293 K and 1 bar), but lower than that of the highest (Mg-MOF-74 = 6.42 mmol g –1 at 1 bar, 298 K).…”

“…58 In particular, IAST calculations say little about separation kinetics since the calculations are derived from single-component gas sorption isotherms that are collected at thermodynamic equilibrium. Therefore, breakthrough experiments were carried out to establish the practical potential of CC3 α for N 2 /SF 6 separations, and in particular to demonstrate that the SF 6 diffusion kinetics are sufficiently fast for real separations.…”

Highly tunable sulfur hexafluoride separation by interpenetration control in metal organic frameworks

“…MD simulations were further performed in the canonical NVT ensemble to explore the diffusivity of the guest molecules in both SIFSIX-2-Cu and SIFSIX-2-Cu-i. The equations of motion were integrated using a leapfrog-type Verlet algorithm [14] and the integration time step was set to 1 fs. The intramolecular geometry of SF6 and N2 molecules was constrained using the quaternion formalism [41].…”

“…Adsorption [4][5][6][10][11][12][13][14][15][16][17] and membrane [8,[18][19][20][21] based-separation have been recently proposed as low energy and cost alternative recovery methods to liquefaction using refrigeration [13]. The efficiency of such processes strongly relies on the choice of the optimal adsorbents combining fast permeability and high thermodynamic selectivity for the gas of interest.…”

“…These findings motivated us to perform a computational exploration of the efficiency of this SIFSIX series of materials for the separation of the SF6/ N2 mixtures at ambient conditions, particularly focusing on the impact of the interpenetrated network. Note that although only a few MOFs have been tested so far for the separation of SF6/ N2 mixtures [4][5][6][10][11][12][13][14][15][16][17], some of them outperform other adsorbents such as zeolites and carbon-based materials [6]. Indeed some studies suggested that MOFs with small pore sizes might be adequate for trapping SF6 at low concentrations whereas MOFs with larger pore sizes will be adequate for the storage of this molecule [6].…”