Crosslinking of Linear Polyimines Into Aminal-Linked Porous Organic Polymers for C₂ Hydrocarbon/Methane Separation

Area of Science:

• Materials Science
• Polymer Chemistry
• Separation Science

Background:

• Hypercrosslinked polymers, or porous organic polymers (POPs), are typically synthesized via Friedel-Crafts alkylation.
• Existing POPs often have limitations in cost and specific adsorption properties.
• Linear polyimines serve as precursors for novel polymer network construction.

Purpose of the Study:

• To develop a new, cost-effective synthesis strategy for porous organic polymers (POPs).
• To investigate the formation of aminal linkages for POP synthesis.
• To evaluate the gas adsorption and separation capabilities of the synthesized POPs.

Main Methods:

• Crosslinking of linear polyimines with m-phenylenediamine via nucleophilic addition to form aminal linkages.
• Characterization of porous organic polymers (POPs) using surface area analysis (BET) and porosity measurements.
• Gas adsorption experiments (C2 hydrocarbons, CO2, CH4) and dynamic breakthrough tests for separation performance evaluation.

Main Results:

• Successfully synthesized aminal-linked POPs with high surface areas (up to 650 m²/g) and significant microporosity.
• The synthesis method is cost-effective (estimated $16/kg) and demonstrates generality across various polyimine structures.
• POPs exhibit high selectivity for C2 hydrocarbons and CO2 over CH4, with excellent separation performance in breakthrough experiments.

Conclusions:

• Nucleophilic addition of amines to imines provides a novel and efficient route to synthesize porous organic polymers (POPs).
• The meta-position of diamines is crucial for effective crosslinking, unlike para-diamines.
• These cost-effective POPs show significant potential for industrial applications in hydrocarbon and CO2 separation.