Michael Guiver

Proton exchange membranes with short-pathway through-plane orientated proton conductivity are highly desirable for use in proton exchange membrane fuel cells. Magnetic field is utilized to create oriented structure in proton exchange membranes. Previously, this has only been carried out by proton nonconductive metal oxide-based fillers. Here, under a strong magnetic field, a proton-conducting paramagnetic complex based on ferrocyanide-coordinated polymer and phosphotungstic acid is used to prepare composite membranes with highly conductive through-plane-aligned proton channels. Gratifyingly, this strategy simultaneously overcomes the high water-solubility of phosphotungstic acid in composite membranes, thereby preventing its leaching and the subsequent loss of membrane conductivity. The ferrocyanide groups in the coordinated polymer, via redox cycle, can continuously consume free radicals, thus helping to improve the long-term in situ membrane durability. The composite membranes exh...

A membrane can be defined broadly as a physical barrier, which allows the selective passage of species from one side to the other under a driving force, or which controls the rate of permeation. Across the spectrum of separations or membrane processes, the species may be organic or aqueous liquids, solutes, vapors, gases, ions or electrons. An example of controlled transport of species is drug delivery. One of the advantages of a membrane process is the avoidance of a phase change, which may typically occur for conventional separation processes. Another advantage is the relatively small footprint of a membrane system, and its scalability and flexibility of onsite “at source” operation, for example, a small water treatment plant (Hoek and Tarabara, 2013; Baker, 2004). The earliest accounts of membrane transport extend back over 200 years, and involved studies on biological as well as some synthetic membranes. Biological membranes are ubiquitous across the plant and animal kingdom, serving a multitude of functions. They have had eons to evolve intricate channels and pore structures and transport mechanisms with exquisite control over the permeation and selective passage of bioactive molecules, ions, water, and gases. In modern membrane science and technology, they serve as inspiration for the design of new membranes, through structural architecture or transport mechanisms. Much earlier work on synthetic membranes was on morphologies that could be thought of as having symmetric or dense structures, which had substantial resistance to transport, resulting in a low transmembrane flux of permeating species. While dense membranes enable the intrinsic properties to be studied in detail, draw useful structure-property relationships, and develop theoretic understanding of transport, they are impractical for industrial separation because of low product permeation. The pivotal point in membrane science occurred in 1961, which was the start of the transformation from academic curiosity to industrial application. This was the development of the first practical membrane with sufficiently high water permeation for desalination of seawater, a process termed “reverse osmosis” (RO). It was an integrally-skinned asymmetric membrane with a thin selective layer made from cellulose acetate, developed by Loeb and Sourirajan, while at the University of California, Los Angeles (UCLA). Shortly after this, Sourirajan moved to the National Research Council (NRC), Canada, at the main Ottawa campus, and established a world-renowned membrane program that was to last several decades (Matsuura, 2020; Lau and Feng, 2021). My long career and interest in membrane research began in January 1981 and spans about 4 decades. Having completed my Master’s degree in natural products chemistry at Carleton University, Canada in 1980, circumstances led me to return to Canada from the United Kingdom in January 1981, and I started a research contract on membrane materials at NRC. During my yearly NRC contracts, I completed my PhD at Carleton University while working at NRC, eventually becoming a Research Officer in 1987, at what was at that time, one of the major hubs Edited and reviewed by: Jong Hak Kim, Yonsei University, South Korea

Membranes for organic solvent nanofiltration (OSN) or solvent-resistant nanofiltration (SRNF) offer unprecedented opportunities for highly efficient and cost-competitive solvent recovery in the pharmaceutical industry. Here, we describe small-flake graphene oxide (SFGO) membranes for high-performance OSN applications. Our strategy exploits lateral dimension control to engineer shorter and less tortuous transport pathways for solvent molecules. By using La3+ as a cross-linker and spacer for intercalation, the SFGO membrane selective layer was stabilized, and size-dependent ultrafast selective molecular transport was achieved. The methanol permeance was up to 2.9-fold higher than its large-flake GO (LFGO) counterpart, with high selectivity toward three organic dyes. More importantly, the SFGO-La3+ membrane demonstrated robust stability for at least 24 hours under hydrodynamic stresses that are representative of realistic OSN operating conditions. These desirable attributes stem from t...

The synthesis of a polymer that combines the processability of plastics with the extreme rigidity of cross-linked organic networks is highly attractive for molecular sieving applications. However, cross-linked networks are typically insoluble or infusible, preventing them from being processed as plastics. Here, we report a solution-processable conjugated microporous thermoset with permanent pores of ~0.4 nm, prepared by a simple heating process. When employed as a two-dimensional molecular sieving membrane for hydrogen separation, the membrane exhibits ultrahigh permeability with good selectivity for H2 over CO2, O2, N2, CH4, C3H6 and C3H8. The combined processability, structural rigidity and easy feasibility make this polymeric membrane promising for large-scale hydrogen separations of commercial and environmental relevance.

Conical-shaped transmembrane protein channels are essential for the transport of ions across lipid bilayers in biological tissues and organisms. Their artificial counterparts are of high applicative interest in biomedical sciences for biomolecule detection and selective ion permeation based on ionic-size and/or charge differences. However, industrial-scale applications such as seawater desalination, separation of mono- from divalent cations, and treatment of highly-saline industrial waste effluents are still big challenges for such biomimetic channels. Here, we report a simple and radically novel "monomer seeding", an experimental approach to grow ionically conductive biomimetic charged nanocone pores at the surface of an acid-functionalized membrane. These readily scalable nanocone membranes enable ultra-fast cation permeation (Na+ = 8.4× vs. Mg2+ = 1.4×) and high ion charge selectivity (Na+/Mg2+ = 6×) compared with the commercial state-of-the-art permselective membrane (CSO, SelemionTM, Japan) due to negligible surface resistances and positively charged conical pore walls, respectively.

Achieving high membrane performance in terms of gas permeance and carbon dioxide selectivity is an important target in carbon capture. Aiming to manipulate the channel affinity towards CO2 to implement efficient separations, gas separation membranes containing CO2 -philic and non-CO2 -philic nanodomains in the interlayer channels of graphene oxide (GO) were formed by intercalating poly(ethylene glycol) diamines (PEGDA). PEGDA reacts with epoxy groups on the GO surface, constructing CO2 -philic nanodomains and rendering a high sorption capacity, whereas unreacted GO surfaces give non-CO2 -philic nanodomains, rendering low-friction diffusion. Owing to the orderly stacking of nanochannels through cross-linking and the heterogeneous nanodomains with moderate CO2 affinity, a GO-PEGDA500 membrane exhibits a high CO2 permeance of 175.5 GPU and a CO2 /CH4 selectivity of 69.5, which is the highest performance reported for dry-state GO-stacking membranes.

Solid electrolytes have attracted much attention due to their great prospects in a number of energy- and environment-related applications including fuel cells. Fast ion transport and superior mechanical properties of solid electrolytes are both of critical significance for these devices to operate with high efficiency and long-term stability. To address a common tradeoff relationship between ionic conductivity and mechanical properties, electrolyte membranes with proton-conducting 2D channels and nacre-inspired architecture are reported. An unprecedented combination of high proton conductivity (326 mS cm(-1) at 80 °C) and superior mechanical properties (tensile strength of 250 MPa) are achieved due to the integration of exceptionally continuous 2D channels and nacre-inspired brick-and-mortar architecture into one materials system. Moreover, the membrane exhibits higher power density than Nafion 212 membrane, but with a comparative weight of only ≈0.1, indicating potential savings in...

The development of polymeric anion-exchange membranes (AEMs) combining high ion conductivity and long-term stability is a major challenge for materials chemistry. AEMs with regularly distributed fixed cationic groups, based on the formation of microporous polymers containing the V-shape rigid Tröger's base units, are reported for the first time. Despite their simple preparation, which involves only two synthetic steps using commercially available precursors, the polymers provide AEMs with exceptional hydroxide conductivity at relatively low ion-exchange capacity, as well as a high swelling resistance and chemical stability. An unprecedented hydroxide conductivity of 164.4 mS cm(-1) is obtained at a relatively a low ion-exchange capacity of 0.82 mmol g(-1) under optimal operating conditions. The exceptional anion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid anion transport.

Rational design of high-performance stable metal–organic framework (MOF) membranes is challenging, especially for the sustainable treatment of hypersaline waters to address critical global environmental issues. Herein, a molecular-level intra-crystalline defect strategy combined with a selective layer thinning protocol is proposed to fabricate robust ultrathin missing-linker UiO-66 (ML-UiO-66) membrane to enable fast water permeation. Besides almost complete salt rejection, high and stable water flux is achieved even under long-term pervaporation operation in hash environments, which effectively addresses challenging stability issues. Then, detailed structural characterizations are employed to identify the type, chemical functionality, and density of intra-crystalline missing-linker defects. Moreover, molecular dynamics simulations shed light on the positive atomistic role of these defects, which are responsible for substantially enhancing structural hydrophilicity and enlarging por...

Carbon molecular sieve (CMS) membranes with rigid and uniform pore structures are ideal candidates for high temperature- and pressure-demanded separations, such as hydrogen purification from the steam methane reforming process. Here, we report a facile and scalable method for the fabrication of cellulose-based asymmetric carbon hollow fiber membranes (CHFMs) with ultramicropores of 3–4 Å for superior H2 separation. The membrane fabrication process does not require complex pretreatments to avoid pore collapse before the carbonization of cellulose precursors. A H2/CO2 selectivity of 83.9 at 130 °C (H2/N2 selectivity of >800, H2/CH4 selectivity of >5700) demonstrates that the membrane provides a precise cutoff to discriminate between small gas molecules (H2) and larger gas molecules. In addition, the membrane exhibits superior mixed gas separation performances combined with water vapor- and high pressure-resistant stability. The present approach for the fabrication of high-perfor...

Membrane distillation (MD) is a promising process for the treatment of highly saline wastewaters. The central component of MD is a stable porous hydrophobic membrane with a large liquid-vapor interface for efficient water vapor transport. A key challenge for current polymeric or hydrophobically modified inorganic membranes is insufficient operating stability, resulting in some issues such as wetting, fouling, flux and rejection decline. This study presents an overall conceptual design and application strategy for a superhydrophobic ceramic‒based carbon nanotube (CNT) desalination membrane having specially designed membrane structures with unprecedented operating stability and MD performance. Superporous and superhydrophobic surface structures with CNT networks are created after quantitative regulation of in situ grown CNT. The fully-covered CNT layers (FC-CNT) exhibit significantly improved thermally and superhydrophobically stable properties under an accelerated stability test. Due...