Construction of Multiple Nonpolar SF₆ Nano-Traps by Highly Stable Pyrazole-Based MOFs for SF₆ Recovery

Area of Science:

• Materials Science
• Environmental Chemistry
• Chemical Engineering

Background:

• Sulfur hexafluoride (SF₆) is a potent greenhouse gas extensively used in electric power systems.
• Efficient separation of SF₆ from N₂ is critical for environmental protection but technologically challenging.
• Adsorptive separation using porous materials offers a promising, yet difficult, solution.

Purpose of the Study:

• To develop novel porous materials for enhanced SF₆/N₂ separation.
• To investigate the structure-property relationships of bipyrazole-based metal-organic frameworks (MOFs) for SF₆ adsorption.
• To achieve high SF₆ uptake, selectivity, and productivity for industrial applications.

Main Methods:

• Synthesis of ultra-stable bipyrazole-based MOFs (M(BPZ), M=Co, Ni, Zn).
• Characterization of MOF properties, including pore structure and surface chemistry.
• Adsorption isotherms, selectivity calculations (IAST), and breakthrough experiments for SF₆/N₂ mixtures.
• Theoretical calculations to elucidate SF₆ adsorption mechanisms.

Main Results:

• Co(BPZ) and Zn(BPZ) exhibited high SF₆ uptakes (2.47 and 2.39 mmol g^-1 at 0.1 bar).
• Co(BPZ) demonstrated superior SF₆/N₂ selectivity (748 at 10/90 v/v) and high SF₆ productivity (46.1 L kg^-1) with ≥99.5% purity.
• Theoretical analysis revealed strong SF₆ adsorption via S-F···π interactions within the MOF channels.

Conclusions:

• Bipyrazole-based MOFs offer a viable strategy for efficient SF₆/N₂ separation.
• The designed nonpolar pore channels with SF₆ nano-traps significantly enhance adsorption affinity.
• This approach provides a facile route for developing advanced adsorbents for greenhouse gas management.