Fluorine Density Gradient Engineering in Triazine-Based Nanoporous Organic Polymers for Highly Selective SF₆ Capture

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Designing effective adsorbents for greenhouse gases like sulfur hexafluoride (SF₆) is crucial for environmental protection.
• Understanding the precise impact of fluorine density on SF₆ adsorption and separation is key for rational adsorbent design.

Purpose of the Study:

• To develop a fluorine density gradient engineering strategy for triazine-based nanoporous polymers (TNOPs).
• To systematically investigate the relationship between fluorine content and SF₆ separation performance.

Main Methods:

• Synthesized a series of TNOPs with varying fluorine content (0-16.34 wt %).
• Characterized the porous structure and fluorine density of the synthesized materials.
• Evaluated SF₆ uptake, adsorption enthalpy, and SF₆/N₂ selectivity using gas adsorption and breakthrough experiments.
• Employed molecular simulations to elucidate interaction mechanisms.

Main Results:

• Increasing fluorine density in TNOPs enhanced SF₆ uptake, isosteric heat of adsorption (Q_st), and SF₆/N₂ selectivity.
• The TNOP-5 material (16.34 wt % F) achieved a high SF₆/N₂ selectivity of 108 at 298 K.
• Molecular simulations indicated that higher fluorine content strengthens key host-guest interactions within ultramicropores.

Conclusions:

• Fluorine density tuning is a practical and effective principle for designing advanced nanoporous adsorbents.
• Optimized fluorine density combined with ultramicropore confinement leads to superior SF₆ separation performance.
• This approach offers a promising pathway for mitigating SF₆ emissions through efficient gas separation.