Temperature-Responsive Xylene Isomer Separation via Biomimetic Window Confinement and Defect-Engineered Nanospace in...

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Biological channels use nanoscale confinement and steric gating for molecular selectivity.
• Metal-organic frameworks (MOFs) offer tunable porous structures for separation applications.

Purpose of the Study:

• To investigate MOF-801 as a biomimetic steric filter for separating xylene isomers.
• To enhance separation performance by introducing structural defects into MOF-801.
• To explore the temperature-dependent selectivity of the modified MOF.

Main Methods:

• Synthesis of defective MOF-801 (MOF-801-132AA).
• Vapor adsorption measurements to determine separation performance and uptake.
• Liquid-batch adsorption, vapor-phase sorption, and breakthrough experiments to validate dynamic behavior.
• Single-crystal electron diffraction and molecular simulations to elucidate separation mechanisms.

Main Results:

• MOF-801-132AA demonstrated high para-xylene (PX) selectivity (PX/ortho-xylene (OX) selectivity of 103.9) and uptake (243.8 mg g⁻¹).
• The material exhibited a temperature-dependent selectivity inversion, favoring PX at lower temperatures and OX at higher temperatures.
• Structural defects enlarged nanospace while preserving window gating, crucial for the observed separation behavior.

Conclusions:

• Defect engineering in MOF-801 can significantly enhance isomer separation performance.
• The interplay of nanospace, window confinement, and isomer packing drives the tunable selectivity.
• This study highlights a strategy for designing MOFs for efficient separation of structurally similar molecules.