Ionic Liquid Selectively Facilitates CO₂ Transport through Graphene Oxide Membrane

Abstract

Membrane separation of CO₂ from H₂, N₂, or CH₄ has economic benefits. However, the trade-off between selectivity and permanence in membrane separation is challenging. Here, we prepared a high-performance CO₂-philic membrane by confining the [BMIM][BF₄] ionic liquid to the nanochannels in a laminated graphene oxide membrane. Nanoconfinement causes the [BMIM][BF₄] cations and anions to stratify. The layered anions facilitate CO₂ transportation with a permeance of 68.5 GPU. The CO₂/H₂, CO₂/CH₄, and CO₂/N₂ selectivities are 24, 234, and 382, respectively, which are up to 7 times higher than that of GO-based membranes and superior to the 2008 Robeson upper bound. Additionally, the resultant membrane has a high-temperature resistance, long-term durability, and high-pressure stability, indicating its great potential for CO₂ separation applications. Nanoconfining an ionic liquid into the two-dimensional nanochannels of a laminated membrane is a promising gas separation method and a nice system for investigating ionic liquid behavior in nanoconfined environments.