A Polymorphic Azobenzene Cage for Energy-Efficient and Highly Selective p-Xylene Separation.

Area of Science:

• Materials Science
• Chemical Engineering
• Organic Chemistry

Background:

• Developing efficient molecular sorbents is crucial for energy-saving applications like C8 separations.
• Existing sorbents often lack the stability, recyclability, or scalability needed for commercial implementation.

Purpose of the Study:

• To develop a novel azobenzene-based cage for selective separation of p-xylene from C8 isomers.
• To assess the material's performance in both vapor and liquid states and its recyclability.

Main Methods:

• Synthesis of an azobenzene-based cage material.
• Testing separation selectivity for C8 isomers in vapor and liquid phases.
• Investigating material stability and regeneration under vacuum.

Main Results:

• The azobenzene-based cage demonstrated high selectivity for p-xylene separation from C8 isomers, outperforming other all-organic sorbents.
• Selective CH-π interactions between azo bonds and xylene molecules were identified as the key separation mechanism.
• The cage exhibited stability in solution and effective regeneration for multiple cycles under vacuum.

Conclusions:

• Azobenzene-based cages represent a promising class of materials for energy-efficient C8 isomer separations.
• The study highlights the potential of azo bonds and guest-induced phase transitions in non-porous organic solids for separation technologies.