Efficient Xe selective separation from Xe/Kr/N₂ mixtures over a microporous CALF-20 framework

Area of Science:

• Materials Science
• Chemistry
• Environmental Science

Background:

• Xenon (Xe) and krypton (Kr) separation is critical for industrial processes and environmental safety, particularly at ambient temperatures.
• Developing efficient adsorbent materials for selective gas capture remains a significant challenge.

Purpose of the Study:

• To synthesize and characterize hydrophobic zinc-based frameworks (CALF-20) for Xe and Kr separation.
• To investigate the adsorptive properties, selectivity, and stability of CALF-20 for Xe, Kr, and N2 mixtures.

Main Methods:

• Synthesis of CALF-20 using 1,2,4-triazole and oxalate ligands with Zn metal centers.
• Characterization of material properties including surface area (442 m²/g) and pore size (6-7 Å).
• Adsorption experiments at 298 K and 1.0 bar to determine uptake, selectivity, adsorption heat, and Henry's constant; computational simulations were also employed.

Main Results:

• CALF-20 exhibits excellent stability in high-temperature acidic solutions.
• Achieved high Xe uptake (2.45 mmol/g) and significant selectivity: Xe/Kr (13.2) and Xe/N2 (62).
• Experimental and simulation data indicate a strong affinity of CALF-20 for Xe, attributed to interactions with C-H groups.

Conclusions:

• CALF-20 is a promising hydrophobic adsorbent for efficient Xe and Kr separation at room temperature.
• The material's properties make it suitable for industrial applications requiring selective noble gas capture.
• The study highlights the potential of tailored metal-organic frameworks for gas separation challenges.