Molecular insight into CO₂/N₂ separation using a 2D-COF supported ionic liquid membrane

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Covalent organic frameworks (COFs) offer potential for gas separation due to their uniform nanopores.
• Existing COFs often have pore sizes misaligned with target gas pairs, limiting selectivity.
• Ionic liquids (ILs) can enhance gas separation but require effective support structures.

Purpose of the Study:

• To develop and investigate a COF-supported ionic liquid membrane (COF-SILM) for efficient CO2/N2 separation.
• To elucidate the molecular mechanisms behind the gas separation performance of COF-SILMs.
• To explore the influence of membrane architecture on separation efficiency.

Main Methods:

• Fabrication of NUS-2 COF-supported ionic liquid membranes (COF-SILMs).
• Molecular dynamics simulations to investigate gas separation performance.
• Analysis of pore size, adsorption, and membrane thickness effects.

Main Results:

• Achieved ultrahigh CO2 permeability (2.317 × 10^6 GPU) and enhanced CO2 selectivity over N2.
• Identified ultrathin membrane, high-density pores, and high transmembrane driving force as key to high permeability.
• Attributed selectivity to differential CO2/N2 adsorption by ILs and a gating effect.

Conclusions:

• COF-SILMs present a promising platform for advanced CO2/N2 separation.
• Molecular dynamics simulations provide critical insights into separation mechanisms.
• Optimized membrane design, including COF layer and IL thickness, can further enhance performance.