Efficient Xe/Kr separation on two Metal-Organic frameworks with distinct pore shapes

A Microporous Hydrogen-Bonded Organic Framework for Efficient Xe/Kr Separation

“…To overcome this dilemma, the emerging crystalline porous materials (CPMs), mainly including metal–organic frameworks (MOFs), , covalent organic frameworks (COFs), and hydrogen-bonded organic frameworks (HOFs), − have received considerable attention because of their exceptional porosity, well-defined pore features, abundant structural tunability, and diverse functionality. − Given the fact that there are no dipole and quadrupole moments of Xe and Kr molecules, therefore, porous material-based gas separation can only be achieved by considering the subtle difference between their kinetic diameters (Xe vs Kr: 4.047 vs 3.655 Å) and polarizabilities (40.44 × 10 –25 and 24.84 × 10 –25 cm 3 for Xe and Kr, respectively). , Theoretical studies suggest that porous MOFs have a tubular channel with optimal pore sizes (4–8 Å) and strong binding sites will be better suitable for Xe/Kr separation. , Most recently, two ultramicroporous MOFs (ATC-Cu and ZJU-74a) have set a new benchmark of Xe/Kr separation in terms of adsorption capacity and selectivity, mainly owing to their optimized pore size and high density of open metal sites. Compared with MOFs and COFs, , HOFs, a new type of porous material with some unique features such as good solution processability, easy purification, and recycling, , are much less investigated for gas separation and purification, − especially for Xe/Kr mixtures.…”

Hydrogen‐Bonded Metal–Nucleobase Frameworks for Efficient Separation of Xenon and Krypton

“…The selectivity of binary gas mixtures of Xe/Kr (20/80, v/v ), Xe/N 2 (1/99, v/v ), Xe/O 2 (1/99, v/v ), and Xe/Ar (1/99, v/v ) for the samples at 298 K and 273 K were calculated based on the Ideal Adsorbed Solution Theory (IAST) (Figure 3e, f, Figure S16, S17, the fitting parameters were listed in Table S4 and S5). The Xe/Kr selectivity of HOF‐ZJU‐201a and HOF‐ZJU‐202a at 298 K was calculated to be 21.0 and 15.1, respectively, which outperforms some top‐performing materials, [18, 31a, d, 32, 34, 40–43] but is lower than CROFOUR‐1‐Ni (22), PAF‐45S (24.1), and Co‐squarate (69.7) [24, 25, 38] …”

An Upper Bound Visualization of Design Trade‐Offs in Adsorbent Materials for Gas Separations: CO2, N2, CH4, H2, O2, Xe, Kr, and Ar Adsorbents

“…The Xe/Kr selectivity versus uptake plot (Figure 16A) interestingly uses Xe/Kr selectivity, which immediately reveals that adsorbent materials studied so far rely on the strength of Xe versus Kr interactions (polarizability 4.04 × 10 −25 and 2.48 × 10 −25 cm −3 , respectively) instead of size selectivity (kinetic diameter 4.1 and 3.6 Å respectively). [ 137 ] Our search only identified one material that was Kr/Xe selective, similar to the CH 4 /H 2 gas pair, where a significant gas size difference was not exploited for size‐sieving under equilibrium conditions.…”