Mass transport at the sub-nanometre scale, including selective transport of gases, liquids and ions, plays a key role in systems such as catalysis, energy generation and storage, chemical sensing and ...molecular separation. Highly efficient biological channels in living organisms have inspired the design of artificial channels with similar, or even higher, mass-transport efficiency, which can be used at a much larger scale. In this Review, we highlight synthetic-nanomaterials-enabled channels in the platforms of well-defined nanopores, 1D nanotubes and 2D nanochannels, and discuss their design principles, channel architectures and membrane or device fabrication. We focus on fundamental mechanisms of sub-nanometre confined mass transport and their relationships with the structure–property–performance. We then present the practicalities of these channels and discuss their potential impact on the development of next-generation sustainable technologies for use in applications related to energy, the environment and healthcare.Artificial channels that selectively transport small molecules at the sub-nanometre scale are used in many applications, but, in particular, in molecular separation. This Review discusses the design of channels, nanostructure, fabrication and mass-transport mechanisms, as well as outlining promising applications and the challenges ahead.
Two‐dimensional (2D) materials of atomic thickness have emerged as nano‐building blocks to develop high‐performance separation membranes that feature unique nanopores and/or nanochannels. These ...2D‐material membranes exhibit extraordinary permeation properties, opening a new avenue to ultra‐fast and highly selective membranes for water and gas separation. Summarized in this Minireview are the latest ground‐breaking studies in 2D‐material membranes as nanosheet and laminar membranes, with a focus on starting materials, nanostructures, and transport properties. Challenges and future directions of 2D‐material membranes for wide implementation are discussed briefly.
Separation goes small: Two‐dimensional materials of atomic thickness have emerged as high‐performance separation membranes. The latest advances in the design and fabrication of 2D‐material membranes are reviewed, along with a discussion about the challenges for future applications.
Graphene-based membranes Liu, Gongping; Jin, Wanqin; Xu, Nanping
Chemical Society reviews,
08/2015, Letnik:
44, Številka:
15
Journal Article
Recenzirano
Graphene is a well-known two-dimensional material that exhibits preeminent electrical, mechanical and thermal properties owing to its unique one-atom-thick structure. Graphene and its derivatives (
...e.g.
, graphene oxide) have become emerging nano-building blocks for separation membranes featuring distinct laminar structures and tunable physicochemical properties. Extraordinary molecular separation properties for purifying water and gases have been demonstrated by graphene-based membranes, which have attracted a huge surge of interest during the past few years. This tutorial review aims to present the latest groundbreaking advances in both the theoretical and experimental chemical science and engineering of graphene-based membranes, including their design, fabrication and application. Special attention will be given to the progresses in processing graphene and its derivatives into separation membranes with three distinct forms: a porous graphene layer, assembled graphene laminates and graphene-based composites. Moreover, critical views on separation mechanisms within graphene-based membranes will be provided based on discussing the effect of inter-layer nanochannels, defects/pores and functional groups on molecular transport. Furthermore, the separation performance of graphene-based membranes applied in pressure filtration, pervaporation and gas separation will be summarized. This article is expected to provide a compact source of relevant and timely information and will be of great interest to all chemists, physicists, materials scientists, engineers and students entering or already working in the field of graphene-based membranes and functional films.
Latest advances in theoretical prediction, fabrication strategies, structure-property relationships, and transport properties of membranes derived from graphene and its derivatives.
Ion transport is crucial for biological systems and membrane-based technology. Atomic-thick two-dimensional materials, especially graphene oxide (GO), have emerged as ideal building blocks for ...developing synthetic membranes for ion transport. However, the exclusion of small ions in a pressured filtration process remains a challenge for GO membranes. Here we report manipulation of membrane surface charge to control ion transport through GO membranes. The highly charged GO membrane surface repels high-valent co-ions owing to its high interaction energy barrier while concomitantly restraining permeation of electrostatically attracted low-valent counter-ions based on balancing overall solution charge. The deliberately regulated surface-charged GO membranes demonstrate remarkable enhancement of ion rejection with intrinsically high water permeance that exceeds the performance limits of state-of-the-art nanofiltration membranes. This facile and scalable surface charge control approach opens opportunities in selective ion transport for the fields of water transport, biomimetic ion channels and biosensors, ion batteries and energy conversions.
As a new family of two-dimensional (2D) materials, MXene, with many attractive physicochemical properties, has attracted increasing attentions and been applied for various applications. Here, for the ...first time, ultrathin MXene membranes with thickness down to several tens of nanometers were developed for pervaporation desalination by stacking synthesized atomic-thin MXene nanosheets. Influences such as lateral size of MXene nanosheets and feed temperature on the resulting membrane performance were systematically investigated. Owing to unique 2D interlayer channels as well as high hydrophilicity, the ultrathin MXene membrane with ~60nm exhibited high water flux (85.4Lm−2h−1) and salt rejection (99.5%) with feed concentration of 3.5wt% NaCl at 65°C. In addition, the MXene membrane showed a good long-term stability and performance in synthetic seawater system. The high-performing ultrathin 2D MXene membrane developed here in this work offers great potential for pervaporation applications.
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•Ultrathin 2D Ti3C2Tx MXene membrane was designed and fabricated.•MXene membrane was first reported for pervaporation process.•Abundant oxygen-containing groups enabled MXene membranes to be hydrophilic.•High water flux (85.4Lm-2h-1) with high salt rejection (99.5%) was realized.
Recent innovations highlight the great potential of two‐dimensional graphene oxide (GO) films in water‐related applications. However, undesirable water‐induced effects, such as the redispersion and ...peeling of stacked GO laminates, greatly limit their performance and impact their practical application. It remains a great challenge to stabilize GO membranes in water. A molecular bridge strategy is reported in which an interlaminar short‐chain molecular bridge generates a robust GO laminate that resists the tendency to swell. Furthermore, an interfacial long‐chain molecular bridge adheres the GO laminate to a porous substrate to increase the mechanical strength of the membrane. By rationally creating and tuning the molecular bridges, the stabilized GO membranes can exhibit outstanding durability in harsh operating conditions, such as cross‐flow, high‐pressure, and long‐term filtration. This general and scalable stabilizing approach for GO membranes provides new opportunities for reliable two‐dimensional laminar films used in aqueous environments.
Graphene oxide membranes are susceptible to water‐induced effects such as peeling of stacked laminates. A strategy is described for stabilization of graphene oxide membranes with interlaminar short‐chain (amine) and interfacial long‐chain (O=CS) molecular bridges. The bridged membranes demonstrate excellent durability in cross‐flow, high‐pressure, and long‐term filtration and they withstand vibration and sonication treatments.
As an alternative energy source to fossil fuels, biobutanol has received increasing attention. In this work, new mixed matrix membranes (MMMs) incorporating zeolitic imidazolate frameworks (ZIF-71) ...particles into polyether-block-amide (PEBA) were prepared for biobutanol recovery from acetone–butanol–ethanol (ABE) fermentation broth by pervaporation (PV). FESEM, EDS, XRD, FT-IR, DSC and contact angle measurements were conducted to study the morphologies, physical and chemical properties and surface properties of the MMMs. The PV performance of the prepared MMMs with various ZIF-71 loadings for separating n-butanol from its aqueous solution was investigated. As a result, both separation factor and thickness-normalized flux of the PEBA membranes were improved by incorporating appropriate amount of ZIF-71 (≤20wt%). The membrane with 20wt% ZIF-71 was evaluated in ABE model solution and ABE fermentation broth, and exhibited high n-butanol separation performance. ZIF-71 particles were confirmed as promising fillers to enhance the separation performance for butanol recovery because of their excellent compatibility with polymer and organophilicity. This work demonstrated the ZIF-71/PEBA MMMs could be potential candidates for practical biobutanol production.
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•Hydrophobic ZIF-71 particles were introduced into PEBA to prepare MMMs.•The MMMs improved separation factor and flux simultaneously in aqueous butanol.•The MMMs showed high butanol recovery performance in ABE fermentation broth.
Graphene oxide (GO) has been considered as a promising material to develop advanced nanofiltration membranes benefiting from its extraordinary physicochemical properties. GO membranes for practical ...application need porous substrates to provide sufficient mechanical strength. Compared to extensive studies on the manipulation of GO selective layer, the influence of substrates on the performance of GO membranes has been received much less attention. Actually, significant differences in physical and chemical properties of the substrates should lead to distinct assembly structure of resulting GO membranes with uneven performance. Therefore, the effect of substrate on GO membranes formation and separation are worth study and optimization. Herein, we employed typical inorganic ceramic tube and polymeric polyacrylonitrile (PAN) and polycarbonate (PC) substrates to support GO membranes and studied the effects of their surface morphologies and roughness, surface chemical composition, as well as bulk pore structure on the formation and nanofiltration performance of resulting GO membranes. Substrates properties were revealed to have remarkable impacts on the adhesion and transport property of GO membranes. We found that the surface morphological and chemical structure of substrates induced GO assembly and determined GO adhesion, and the bulk pore structure of substrates dominated the whole transport resistance of GO membrane. Especially, the PAN substrate possessing abundant oxidized functional groups after simple hydrolysis, contributed to a robust interfacial adhesion with GO selective layer and enabled GO membrane to withstand harsh stability measurements including cross-flow, high feed pressure and long-period continuous operation. Besides, the smooth surface morphology along with the bulk highly porous structure of PAN substrate offered a favorable platform for GO assembly, resulting in competitive nanofiltration performance with water permeance of 15.5 Lm−2 h−1bar−1 and dye rejection of 99.5%. Overall, this work gives new insights of design and fabrication of durable GO membranes for practical applications.
•Surface morphology and chemical structure of substrates control GO layer formation.•Bulk pore structure of substrates dominates transport resistance of GO membrane.•Hydrolyzed PAN substrate optimizes formation and NF performance of GO membranes.
Membrane-based separations can improve energy efficiency and reduce the environmental impacts associated with traditional approaches. Nevertheless, many challenges must be overcome to design ...membranes that can replace conventional gas separation processes. Here, we report on the incorporation of engineered submicrometre-sized metal-organic framework (MOF) crystals into polymers to form hybrid materials that successfully translate the excellent molecular sieving properties of face-centred cubic (fcu)-MOFs into the resultant membranes. We demonstrate, simultaneously, exceptionally enhanced separation performance in hybrid membranes for two challenging and economically important applications: the removal of CO
and H
S from natural gas and the separation of butane isomers. Notably, the membrane molecular sieving properties demonstrate that the deliberately regulated and contracted MOF pore-aperture size can discriminate between molecular pairs. The improved performance results from precise control of the linkers delimiting the triangular window, which is the sole entrance to the fcu-MOF pore. This rational-design hybrid approach provides a general toolbox for enhancing the transport properties of advanced membranes bearing molecular sieve fillers with sub-nanometre-sized pore-apertures.
Ion transport is crucial for biological systems and membrane-based technologies from both fundamental and practical aspects. Unlike biological ion channels, realizing efficient ion sieving by using ...membranes with artificial ion channels remains an extremely challenging task. Inspired by biological ion channels with proper steric containment of target ions within affinitive binding sites along the selective filter, herein we design a system of biomimic two-dimensional (2D) ionic transport channels based on a graphene oxide (GO) membrane, where the ionic imidazole group tunes the appropriate physical confinement of 2D ionic transport channels to mimic the confined cavity structures of the biological selectivity filter, and the ionic sulfonic group creates a favorable chemical environment of 2D ionic transport channels to mimic the affinitive binding sites of the biological selectivity filter. As a result, the as-fabricated ionic GO membrane demonstrates an exceptional K+ transport rate of ∼1.36 mol m–2 h–1 and competitive K+/Mg2+ selectivity of ∼9.11, outperforming state-of-the-art counterparts. Moreover, the semiquantitative studies of ion transport through 2D ionic transport channels suggest that efficient ion sieving with the ionic GO membrane is achieved by the high diffusion and partition coefficients of hydrated monovalent ions, as well as the large energy barrier and limited potential gradient of hydrated divalent ions encountered.
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