Subnanometer Two-Dimensional Graphene Oxide Channels for Ultrafast Gas Sieving

Abstract

Two-dimensional (2D) materials with atomic thickness and extraordinary physicochemical properties exhibit unique mass transport behaviors, enabling them as emerging nanobuilding blocks for separation membranes. Engineering 2D materials into membrane with subnanometer apertures for precise molecular sieving remains a great challenge. Here, we report rational-designing external forces to precisely manipulate nanoarchitecture of graphene oxide (GO)-assembled 2D channels with interlayer height of ∼0.4 nm for fast transporting and selective sieving gases. The external forces are synergistic to direct the GO nanosheets stacking so as to realize delicate size-tailoring of in-plane slit-like pores and plane-to-plane interlayer-galleries. The 2D channels endow GO membrane with excellent molecular-sieving characteristics that offer 2-3 orders of magnitude higher H2 permeability and 3-fold enhancement in H2/CO2 selectivity compared with commercial membranes. Formation mechanism of 2D channels is proposed on the basis of the driving forces, nanostructures, and transport behaviors.

A Regularly Channeled Lamellar Membrane for Unparalleled Water and Organics Permeation

“…The K' value for MXene membrane (10 À8.5 )isover five orders of magnitude higher than that of GO membrane (10 À13.8 ), highlighting an ultralow transport barrier through MXene channels.C onsidering as harp decline in water permeance even after small disturbance of water-bonded flow, [4] these regular and straight channels have proven to be the most efficient transfer pathways to assure low-barrier molecular transfer. [5] As summarized in Figure 3dand the Supporting Information, Table S1, the MXene membrane exhibits an exceptional water separation performance,w hich outperforms almost all of the lamellar membranes including GO, WS 2 ,and MoS 2 , [2,15] highlighting the superiority of regular and straight transport channels. This observation can also be confirmed by the boosted K' value (10 À12.6 )o fG Om embrane when improving channel regularity (Supporting Information, Figure S23).…”

“…[2a] It is recognized that the fast transport of molecules relies on continuum pore-flow transportation and molecularly ordered flow through interlayer channels. [5] Moreover,r egular channels with narrow width distribution are also essential for high membrane rejection that is based on the size-exclusion effect. [4] Thus,r egular and straight interlayer channels,which permit continuous and steady molecular-flow are essential for the fast transport.…”

“…Moreover,t he sheet stacking is ordered and uniform with regular and straight interlayer channels, sharply contrasting to the winded and curled ones in GO laminate (Supporting Information, Figure S9). [5] Amorphous anodic aluminum oxide (AAO) was utilized as as upport to minimize its interference. Theregularity degree of interlayer channels in membrane was probed by XRD.…”

Boron Nitride Membranes with a Distinct Nanoconfinement Effect for Efficient Ethylene/Ethane Separation

“…[3] Them ole-cule transport through GO membranes relies on slit-like nanopore permeation, followed by plane-to-plane nanochannel flow.B yf ine-tuning the sizes of slit-like nanopores and nanochannels,G Om embranes can achieve tunable gas separation performances for different gas pairs,s uch as H 2 / CO 2 ,H 2 /N 2 ,C O 2 /CH 4 ,o rC O 2 /N 2 . [5] Boron nitride (BN) nanosheets,a lso referred to as white graphene,consist of afew layers of atomically thin hexagonal BN planes and share as imilar structure with graphene, [6] which have anumber of applications such as electrochemical energy conversion and storage,e lectrocatalysts,f lexible electronics,a nd biomedicine. [5] Boron nitride (BN) nanosheets,a lso referred to as white graphene,consist of afew layers of atomically thin hexagonal BN planes and share as imilar structure with graphene, [6] which have anumber of applications such as electrochemical energy conversion and storage,e lectrocatalysts,f lexible electronics,a nd biomedicine.…”

Graphene oxide membrane for molecular separation: challenges and opportunities

“…Fast and selective gas permeation through fewlayered GO membranes [7,8] or GO incorporated polymer hybrid membranes [14] were also reported for separating gas pairs such as H 2 /CO 2 and CO 2 /N 2 , in which subnanosized transport channels were provided by structural defects and/or interlayer galleries of GO nanosheets. We introduced external forces by using vacuum spinning technique combined with layer-by-layer molecular intercalation, to precisely manipulate the 2D channels of GO membranes for fast transporting and selective sieving gases [15]. The external forces are synergistic to regulate the stacking behavior of GO nanosheets so as to realize delicate size-tailoring of in-plane slit-like pores and plane-to-plane interlayer-galleries.…”