Tuning flexibility to control selectivity in soft porous crystals

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Chemistry

Background:

• Soft porous crystals (SPCs) exhibit tunable pore sizes, enabling selective adsorption.
• Polymorphism in mesoporous SPCs allows transitions between narrow and large pore phases.
• Supercritical fluid adsorption is crucial for separation technologies.

Purpose of the Study:

• Investigate the impact of SPC flexibility on selective adsorption of size-asymmetric supercritical fluids.
• Analyze how pore size polymorphism influences adsorption selectivity.
• Explore strategies for tuning SPC behavior for enhanced separation.

Main Methods:

• Flat-histogram Monte Carlo simulations were employed.
• Mesoporous SPCs with multiple free energy minima were modeled.
• Selectivity curves as a function of adsorbate pressure were analyzed.

Main Results:

• SPC flexibility significantly alters the relative stability of pore phases, tuning overall selectivity.
• Gate-opening SPCs show more pronounced control over selectivity via flexibility compared to breathing materials.
• Breathing SPCs can be engineered for multiple adsorption/desorption cycles.

Conclusions:

• Material flexibility is a key parameter for controlling selective adsorption in SPCs.
• Understanding pore phase transitions is essential for designing advanced separation materials.
• This work provides a framework for designing flexible porous materials for targeted supercritical fluid separations.