Ion-Gated Gas Separation through Porous Graphene

Abstract

Porous graphene holds great promise as a one-atom-thin, high-permeance membrane for gas separation, but to precisely control the pore size down to 3-5 Å proves challenging. Here we propose an ion-gated graphene membrane comprising a monolayer of ionic liquid-coated porous graphene to dynamically modulate the pore size to achieve selective gas separation. This approach enables the otherwise nonselective large pores on the order of 1 nm in size to be selective for gases whose diameters range from 3 to 4 Å. We show from molecular dynamics simulations that CO, N, and CH all can permeate through a 6 Å nanopore in graphene without any selectivity. But when a monolayer of [emim][BF] ionic liquid (IL) is deposited on the porous graphene, CO has much higher permeance than the other two gases. We find that the anion dynamically modulates the pore size by hovering above the pore and provides affinity for CO, while the larger cation (which cannot go through the pore) holds the anion in place via electrostatic attraction. This composite membrane is especially promising for CO/CH separation, yielding a CO/CH selectivity of about 42 and CO permeance of ∼10 GPU (gas permeation unit). We further demonstrate that selectivity and permeance can be tuned by the anion size, pore size, and IL thickness. The present work points toward a promising direction of using the atom-thin ionic liquid/porous graphene hybrid membrane for high-permeance, selective gas separation that allows a greater flexibility in substrate pore size control.

Combining Silk Sericin and Surface Micropatterns in Bacterial Cellulose Dressings to Control Fibrosis and Enhance Wound Healing

“…2b). 52 For instance, Jiang's group 53 computationally deposited a layer of ionic liquid-(emim)(BF 4 ) onto H-terminated porous graphene having 1 nm pores (Fig. 2c).…”

Two‐Dimensional Materials as Prospective Scaffolds for Mixed‐Matrix Membrane‐Based CO2 Separation

“…The discovery of graphene, a single‐atomic‐layer honeycomb lattice of carbon atoms in an sp 2 hexagonal bonding configuration, has inspired an extensive search for novel 2D materials with a wide variety of promising applications in materials science, chemistry, and condensed matter physics . Among them, the use as a versatile new platform for membrane‐based separation technology has drawn significant research interests owing to their unique atomic structures .…”

“…By employing a commercially available support, polyethersulfone membrane, high CO 2 /N 2 selectivity was successfully achieved for the resultant GO membrane in high relative humidity, suggesting the promising application of GO‐based membranes in post‐combustion CO 2 capture processes. At the same time, Li and his co‐workers reported a vacuum‐filtration approach towards the synthesis of ultrathin GO membranes . Anodic aluminium oxide was selectively employed as the membrane support.…”

Insights on the mechanism of water-alcohol separation in multilayer graphene oxide membranes: Entropic versus enthalpic factors

“…Theoretical studies devoted to understand the water filtration mechanisms inside GO membranes came mostly from studies dedicated to water desalination 13 , while very few works have been dedicated to water-alcohol separation. The separation mechanism has been attributed to the formation of a network of nano-capillaries that allow nearly frictionless water flow, while blocking other molecules by steric effects 4 .…”