Synthesizing Hypercrosslinked Polymers with Deep Eutectic Solvents to Enhance CO₂/N₂ Selectivity

Area of Science:

• Polymer Chemistry
• Materials Science
• Green Chemistry

Background:

• Hypercrosslinked polymers (HCPs) are vital for applications like ion exchange and gas separation.
• Traditional HCP synthesis relies on toxic halogenated solvents, posing environmental and health risks.

Purpose of the Study:

• To investigate the feasibility of replacing hazardous halogenated solvents with deep eutectic solvents (DES) in HCP synthesis.
• To explore the efficacy of DES as both solvent and catalyst in Friedel Crafts alkylation for polymer crosslinking.

Main Methods:

• Synthesized HCPs using two distinct DES formulations: [ChCl][ZnCl2]2 and [ChCl][FeCl3]2.
• Employed both internal and external crosslinking strategies.
• Characterized the synthesized HCPs, focusing on surface area, pore size distribution, and gas selectivity.

Main Results:

• HCPs synthesized in DES exhibited 20-60% lower specific surface areas compared to those made with halogenated solvents.
• CO2/N2 selectivities were significantly enhanced, reaching up to 453% higher values.
• The poly-α,α'-dichloro-p-xylene synthesized in [ChCl][ZnCl2]2 via internal crosslinking achieved a CO2/N2 selectivity of 105.

Conclusions:

• Deep eutectic solvents provide a viable, greener alternative to halogenated solvents for HCP synthesis.
• HCPs synthesized in DES possess narrower pore size distributions, leading to improved gas separation performance, particularly for CO2/N2 selectivity.