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Fabrication of crystalline, robust covalent organic framework (COF) membranes based on disorder‐to‐order strategy is promising yet highly challenging. Herein, a microwave‐assisted method for fabricating COF membranes is proposed. Initially, monomers polymerize rapidly on the surface of porous Al2O3 substrate at room temperature to form an amorphous pristine membrane. Subsequently, a microwave field is exerted to trigger fast crystallization, acquiring a crystalline COF membrane within 60 min. The amorphous pristine membrane exhibits a high dissipation factor, indicating excellent microwave absorption capability, which accelerates the dynamic reversible reactions during the microwave treatment and thus ensures a rapid transition from the amorphous to the crystalline state. Owing to the high‐crystallinity and robust structure, the COF membranes exhibit high rejection rates for solute molecules with molecular weights exceeding 700 Da (e.g., Evans blue: 98.7%) and high solvent permeance for organic solvents (e.g., ethanol: 87.8 Lm−2h−1 bar−1, n‐hexane: 222.3 Lm−2h−1 bar−1). Surprisingly, the COF membranes exhibit superior mechanical properties, with Young's modulus of 33.91 ± 3.94 GPa, outperforming previously reported polycrystalline COF membranes and are close to those for inorganic zeolite membranes. The microwave‐assisted COF crystallization method opens a new avenue to fabricating a variety of crystalline membranes for advanced separations. [ABSTRACT FROM AUTHOR]

A key challenge in efficient molecular separation is fabricating large‐scale, highly selective polymeric membranes with precise pore control at the molecular scale. Herein, a new contorted monomer 6,6′‐dihydroxy‐2,2′‐biphenyldiamine (DHBIPDA) is introduced as a building block to generate cross‐linked, ultra‐thin microporous nanofilms (sub‐10 nm) via interfacial polymerization, enabling rapid, and precise molecular nanofiltration. Using diacyl chloride (TPC) as the cross‐linker instead of trimesoyl chloride (TMC) significantly reduces the pore sizes within the membranes and achieves a narrower pore distribution due to a semi‐crystalline structure. The film structures are confirmed using comprehensive characterization techniques including wide‐angle X‐ray scattering (WAXS), X‐ray diffraction (XRD), positron annihilation lifetime spectroscopy (PALS), CO2 adsorption analysis, and molecular‐scale simulation. The DHBIPDA/TPC and DHBIPDA/TMC membranes achieve methanol permeance values of up to 16.4 and 15.1 LMH bar−1 coupled with molecular weight cutoffs (MWCOs) as low as 283 and 306 Da, respectively. The DHBIPDA/TPC membrane demonstrates both higher permeance and higher selectivity compared to its relatively disordered counterpart DHBIPDA/TMC, consistent with characterization data. The DHBIPDA‐derived membrane efficiently separates dye mixtures with similar molecular weights and enables effective recycling of organometallic homogeneous catalysts, suggesting its potential for industrial applications. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs), known for their chemical stability and porous crystalline structure, hold promises as advanced separation membranes. However, fabricating high‐quality COF membranes, particularly on industrial‐preferred hollow fiber substrates, remains challenging. This study introduces a novel vapor/vapor‐solid (V/V−S) method for growing ultrathin crystalline TpPa‐1 COF membranes on the inner lumen surface of alumina hollow fibers (TpPa‐1/Alumina). Through vapor‐phase monomer introduction onto polydopamine‐modified alumina at 170 °C and 1 atm, efficient polymerization and crystallization occur at the confined V−S interface. This enables one‐step growth within 8 h, producing 100 nm thick COF membranes with strong substrate adhesion. TpPa‐1/Alumina exhibits exceptional stability and performance over 80 h in continuous cross‐flow organic solvent nanofiltration (OSN), with methanol permeance of about 200 L m−2 h−1 bar−1 and dye rejection with molecular weight cutoff (MWCO) of approximately 700 Da. Moreover, the versatile V/V−S method synthesizes two additional COF membranes (TpPa2Cl/Alumina and TpHz/Alumina) with different pore sizes and chemical environments. Adjusting the COF membrane thickness between 100–500 nm is achievable easily by varying the growth cycle numbers. Notably, TpPa2Cl/Alumina demonstrates excellent OSN performance in separating the model active pharmaceutical ingredient glycyrrhizic acid (GA) from dimethyl sulfoxide (DMSO), highlighting the method's potential for large‐scale industrial applications. [ABSTRACT FROM AUTHOR]

Nanoporous graphene is promising for the fabrication of high-performance organic solvent nanofiltration (OSN) membranes owing to the excellent chemical resistance of graphene in organic solvents. Moreover, the nanopores increase solvent permeance by providing diffusion channels. However, conventional chemical and physical etching methods are generally applicable on a laboratory-scale, and the large-scale fabrication of these structures is challenging. Herein, a large-area nanoporous multilayer graphene oxide (NMG) membrane was prepared using a combination of slot-die coating and confined thermal treatment. Graphene oxide (GO) was coated on polymeric supports using a slot-die coater, which is generally used for continuous coating in industry. Afterward, the GO membrane was treated using a hot-pressing method to activate the nanopores on the graphene surface and weld the polymeric support with the graphene layer. The interlayer and pore structure of GO were tuned by modulating the hot-pressing time, and its influence on OSN performance was systemically investigated. The optimized NMG membrane exhibited a high ethanol permeance of 300 Lm−2h−1bar−1 and a sharp molecular weight cut-off of 500 g/mol. Furthermore , the enhanced adhesion between graphene and the polymeric support enables mechanically stable membrane operation under cross-flow conditions for 30 days, which is the longest test time reported for two-dimensional material-based OSN membranes thus far. [Display omitted] [ABSTRACT FROM AUTHOR]

Microporous organic polymers (MOPs) featuring chemically rigid backbones and permanent micropores are desirable for fabricating molecular selective membranes towards organics separation. However, coordinating facile film processing with high micropore persistence remains a challenge. In this paper, a low molecular weight polymers of intrinsic microporosity was rationally designed by precisely controlling the stoichiometric equilibrium of polymerization monomer. The polymers of intrinsic microporosity oligomers combine rigid and contorted structures with the aqueous solution processability, promoting the formation of 25-nm-thick polyaramide nanofilms with enhanced microporosity via support-free interfacial polymerization (SFIP). The resulting composite membranes have superior retention of small molecular solutes and high nonpolar and polar solvent permeances. Experiment and simulation results show that their excellent separation performance is due to substantially open and interconnected microporosity formed in the polymer networks based on rigid and contorted diamines as well as reduced film thickness. This study provides a new sight for using MOPs to construct high-microporosity membranes for precise and rapid molecular sieving. [Display omitted] • A novel rigid molecule that polymers of intrinsic microporosity oligomer (APIMO) was rationally designed. • APIMO was employed as the building block for constructing thin film via support-free interfacial polymerization. • The resultant thin film composite membrane displayed superior permeances of both nonpolar and polar solvents. [ABSTRACT FROM AUTHOR]

Semi-crystalline poly (ether ketone) (PEK) materials with intrinsic solvent resistance are ideal materials for the preparation of organic solvent nanofiltration (OSN) membranes. Although some precursor materials have been developed for soluble processing through group protection strategies, these precursors are difficult to hydrolyze, limiting their practical applications. In this work, we designed an easily hydrolyzable N-cyclohexyl-poly (ether ketone ether imide) (CYH-PEKEI) precursor that could be converted to PEK by acid treatment at 80°C within 1 h. The results showed that the prepared membrane was stable in various organic solvents, with a permeance of 1.29 L m−2 h−1 bar−1 in N, N-Dimethylformamide (DMF), a molecular weight cutoff of 320 g/mol, and good long-term operational stability. Additionally, the membrane demonstrated excellent aging resistance during variable temperature DMF operation. This work has stimulated the potential of PEK membranes for OSN applications by optimizing the precursor structure. [Display omitted] • A soluble and processable PEK precursor polymer was synthesized. • The solvent-resistant PEK membrane can be obtained through a simple and rapid acid treatment. • The PEK membrane is capable of long-term operation in DMF solvent. • The PEK membrane exhibits excellent aging resistance and thermal stability. [ABSTRACT FROM AUTHOR]

For thin-film composite (TFC) membranes applied in organic solvent nanofiltration (OSN), enhancing the adhesion between the active layers and the substrates can effectively improve the stability of the membranes. In this work, TFC OSN membranes with polyetherketone bearing amino group (PEK-NH 2) asymmetric substrates and amino-contained polyarylate active layers were fabricated by interfacial polymerization technique, and subsequently reacted with dialdehydes to form crosslinking between and within the substrates and the active layers. Crosslinking improved both of the solvent resistance of the substrates and the separation selectivity of the active layers. In addition, reverse pressure testing demonstrated that crosslinking allowed the active layers to adhere more strongly to the substrates. The optimized integrally crosslinked membranes exhibited methanol permeance of 10.4 L m−2 h−1 bar−1 and a molecular weight cut-off of about 320 g mol−1 in methanol. Moreover, the integrally crosslinked membranes maintained good stability for OSN operation in methanol for 12 days, and also exhibited unchanged OSN performance after soaked in N,N -dimethylformamide for 2 days. This work demonstrated a novel solvent-resistant membrane material and membrane-fabrication strategy with prospect for OSN application. Schematic illustration of integrally crosslinking. [Display omitted] • Glutaraldehyde reacts with amino groups both in two layers to achieve integrally crosslinking. • Crosslinking within the active layer enhances the selectivity of the TFC membrane. • The adhesion between the active layer and the substrate is enhanced by integrally crosslinking. • The membrane shows methanol permeance of 10.4 L m−2 h−1 bar−1 with MWCO down to 320 g mol−1. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs), with their regularly organized structures and solvent resistance, offer distinct advantages for constructing liquid-phase separation membranes. In nearly a decade of development, research has mainly focused on two-dimensional (2D) COFs, which yet give insufficient molecular selectivity due to inherent large pores. Here, we present a mixed-dimensional strategy of growing three-dimensional (3D) COFs on 2D COFs to build bilayered membranes for efficient organic solvent nanofiltration (OSN). The pores of 3D COFs interlace with those of 2D counterparts, resulting in a subnanoporous composite. We develop this 3D-/2D-COFs composite as robust membranes with a nanoscale thickness. The optimal bilayered membrane yields ethanol permeance of 12.2 L m−2 h−1 bar−1 with a molecular weight cutoff as low as ∼400 g mol−1, surpassing conventional COF-based OSN membranes. Importantly, the designed 3D-/2D-COFs membrane exhibits stable separation performance and excellent sieving ability to discriminate molecular mixtures. This exceptional molecular selectivity ultimately allows the separation of bioactive pharmaceuticals from impurities through our membrane. Overall, this work provides a design strategy for producing mixed-dimensional COF membranes to advance molecular separation in liquids. [Display omitted] • Mixed-dimensional covalent organic framework composites show reduced pore sizes. • Robust membranes of mixed-dimensional covalent organic frameworks are developed. • The optimal membrane exhibits high molecular selectivity with substantial permeances. • Our membrane performs high-selectivity purification of pharmaceuticals from impurities. [ABSTRACT FROM AUTHOR]

Microporous polymer frameworks have attracted considerable attention to make novel separation layers owing to their highly porous structure, high permeability, and excellent molecular separation. This study concerns the fabrication and properties of thin melamine‐based microporous polymer networks with a layer thickness of around 400 nm, supported on an α‐alumina support and their potential use in organic solvent nanofiltration. The modified membranes show excellent solvent purification performances, such as n‐heptane permeability as high as 9.2 L m−2 h−1 bar −1 in combination with a very high rejection of approximately 99 % for organic dyes with molecular weight of ≥457 Da. These values are higher than for the majority of the state‐of‐the‐art membranes. The membranes further exhibit outstanding long‐term operation stability. This work significantly expands the possibilities of using ceramic membranes in organic solvent nanofiltration. [ABSTRACT FROM AUTHOR]

• Ethanolic solvents induced high-yield antioxidant extraction from Sideritis. • Ultrasound assisted extraction resulted more efficient than conventional methods. • Joint use of ultrasound and nanofiltration resulted in a high-value extract. Sideritis scardica and Sideritis syriaca are considered highly valuable plant materials and their total polyphenols (TP) and total flavonoids (TF) extracts can be employed in nutraceutics and cosmetics. A two-step process was proposed consisting in the ultrasound-assisted extraction (UAE) and concentration of the biologically active compounds via nanofiltration (NF). An extensive comparison between UAE and conventional high-temperature stirring was performed, taking into account the effect of process parameters such as solvent, temperature and ultrasonication. In terms of radical scavenging activity and time optimization, UAE was found more effective, providing – after only 1 h – extraction yields comparable to 20 h of the conventional thermo-mechanical method. The extract was then concentrated by nanofiltration in tangential mode at 20 bar using 300 and 500 Da cut-off Duramem membranes. Permeate and rejection flux was monitored during the filtration process. The lower molecular weight membrane showed higher permeability towards TP and TF and contributed to a more stable flux and lower fouling processes. To predict operational drawbacks, computational fluid dynamic simulations were performed to model the complex rotational flow occurring during membrane filtration. [ABSTRACT FROM AUTHOR]

Abstract We have developed stable organic solvent nanofiltration (OSN) membranes that are electrically conductive. These membranes overcome key issues with current tuneable membranes: molecular weight cut off (MWCO) limited to the UF-range and lack of filtration stability. Polyaniline (PANI) was in-situ doped by poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) using chemical oxidative polymerization that leads to formation of interpolymer complex. The PANI-PAMPSA membranes were prepared by phase inversion method and the pore sizes were shrunk by annealing the membranes at temperatures lower than the crosslinking temperature. The membranes were systematically evaluated using visual and chemical analysis and in-filtration experiments. The developed membranes were solvent stable, reusable, had a denser structure and lower MWCO and there was no thermal crosslinking as seen by IR. The solvent permeance obtained were: 0.46, 0.60 and 0.74 Lm−2h−1bar−1 for acetone, 2-propanol and methanol respectively, with MWCO below 300 Da and 266 Da for methanol. For the tuneability investigation, when applying an electrical potential (20 V) in a custom-made cross-flow membrane cell, an increase in MWCO and permeance (10.4% and 55.6%, respectively) was observed. These results show that this simple in-situ doping method with heat treatment can produce promising and stable PANI membranes, for OSN processes in different solvents, with the distinctive feature of in-situ performance control by applying external electrical potential. Graphical abstract Image 1 Highlights • Robust organic solvent nanofiltration membranes have been prepared. • Heat treated membrane had MWCOs lower than 300 Da for all tested solvents. • PANI-PAMPSA membranes showed electrical tuneability. • The application of 20 V potential increased the permeance by 55.6%. [ABSTRACT FROM AUTHOR]

To expand industrial utilizations, membranes with fast transport of organic solvents and precision molecular separation, along with strong chemical stability, have great potential for minimizing energy consumption in separation processes. In this study, novel amino-cyclodextrin organic solvent nanofiltration (OSN) membranes containing P84 polymer were successfully fabricated using amino-cyclodextrin and amino-5-guanidinopentanoic acid (DL-A) as monomers through a two-step green modification process. The resulting membranes exhibit high stability in harsh organic solvents, such as dimethylsulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP), with a weight loss of less than 5 % after 30 days of immersion. These membranes also demonstrate rapid solvent transport for both polar solvents, such as methanol (86.56 L m−2 h−1 bar−1), and nonpolar solvents, such as n-hexane (48.97 L m−2 h−1 bar−1), along with high dye rejections. Additionally, the membranes possess rigid nanopores structures and consistent rejections across different pressures and solute concentrations. Most importantly, the newly synthesized amino-cyclodextrin OSN membranes are capable of separating molecules based on their 3D structures, particularly those with relatively similar molecular weights. Comparing to those reported cyclodextrin-based membranes, the newly developed amino-cyclodextrin OSN membranes show significant improvements in permeance for both polar and nonpolar organic solvents, while maintaining comparable dye rejection capabilities. The combination of fast solvent transport, excellent chemical stability, and shape selectivity makes these membranes highly promising for high-performance molecular separation in various industrial applications. [Display omitted] • A novel P84 co-polyimide organic solvent nanofiltration (OSN) membrane incorporated with amino-beta-cyclodextrin, was prepared. • The amino-β-cyclodextrin-based membrane has faster solvent transport for both polar and nonpolar solvents. • The amino-β-cyclodextrin-based membrane exhibits excellent stability in harsh organic solvents. • The newly synthesized amino-cyclodextrin OSN membrane demonstrates excellent shape selectivity to solutes with similar molecular weights. [ABSTRACT FROM AUTHOR]

[Display omitted] • TFC membranes with PEEK support and biphenyl polyamides active layer were fabricated for the first time. • Biphenyl polyamide nanofilms exhibited enhanced nano-mechanical strength, high solvent stability and regulated morphology. • The optimized membrane exhibited a high permeability for acetonitrile of 21.6 L m-2 h-1 bar-1. • MWCOs of the membranes can be customized between 170 to 370 g·mol−1 by employing appropriate biphenyl acyl chlorides. Developing polymeric separation membranes that combine excellent solvent stability, high permeability, and customizable molecular weight interception remains a challenge. Herein, thin-film composite (TFC) polyamide (PA) membranes with poly(ether ether ketone) (PEEK) support and biphenyl-centered polyamides active layer were fabricated through interfacial polymerization technique for the first time. Enhanced solvent stability was exhibited by the fabricated membranes due to the intrinsic resistance to organic solvents possessed by PEEK and biphenyl polyamides. The separation performance of the obtained membranes was systematically studied by relating to the properties of PA nanofilms in terms of nano-mechanical strength, morphologies, and microporosity. The organic solvent nanofiltration (OSN) performance of the resultant membranes in terms of permeability and molecular weight cut-off (MWCO) could be regulated. The optimized membrane exhibited a pure solvent permeability as high as 21.6 L m−2 h−1 bar−1 for acetonitrile and 14.0 L m−2 h−1 bar−1 for methanol. It also showed excellent long-term durability with almost unchanged permeability as well as solute retention remained above 97.8 % after a cumulative OSN operation of N, N -Dimethylformamide (DMF) based feed for 240 h. In particular, OSN membrane with targeted MWCOs covering the range of 170–370 g·mol−1 could be fabricated by selecting appropriate biphenyl acyl chlorides as building blocks. This approach offers a scalable and versatile platform for the development of solvent-stable, highly permeable, and customizable MWCO membranes for process-oriented OSN. [ABSTRACT FROM AUTHOR]

An ultrathin graphene oxide (GO) laminar composite membrane has been fabricated in-house via pressure-assisted filtration. It has a relatively high pure water permeability (PWP) of 7.70 LMH/bar with a molecular weight cut-off (MWCO) of 1243 Da. When being treated with various solvents, the membrane exhibits good stability in both polar and nonpolar solvents. The GO laminar composite membrane has relatively high pure solvent fluxes of 24.89 Lm −2 h −1 , 7.95 Lm −2 h −1 and 12.08 Lm −2 h −1 for ethanol, isopropanol and hexane, respectively. Its rejections to orange II sodium salt, safranin O, solvent blue 35, rhodamine B and remazol brilliant blue are 56.60%, 86.52%, 4.39%, 66.95% and 97.11%, respectively. Experimental results suggest that the Donnan exclusion is less effective in organic solvent nanofiltration (OSN) than in aqueous systems, while the size exclusion and solute-membrane affinity are the dominant factors in determining separation performance. Some active pharmaceutical ingredients (APIs) and food additives, e.g. tetracycline, rifampicin, roxithromycin, spiramycin, vitamin B12 and lecithin, are used to demonstrate the separation capability of the newly developed membrane in real-life applications. It can effectively retain those compounds with rejections of 65.80%, 82.67%, 84.27%, 92.21%, 95.34% and 98.44%, respectively. Several 7-day tests of vitamin B12 in isopropanol also confirm the membrane integrity and separation performance for continuous OSN uses. [ABSTRACT FROM AUTHOR]

Covalent organic polymers (COPs) with abundant micropores are deemed as promising materials for building molecular separation membranes. In spite of this potential, fabricating COP separation membranes through an efficient and scalable method remains a significant challenge. Herein, we report a simple and efficient strategy for the synthesis of COP membranes with three-dimensionally interconnected micropores. Utilizing transition-metal nitrates as a catalyst, we achieve fast polymerization of amorphous COPs with relatively uniform micropores (0.7 nm in diameter). The rational design of organic-aqueous interface allows for the direct fabrication of robust COP membranes with an ultrathin thickness of ∼20 nm on porous polyacrylonitrile substrates. The resulting hydrophobic but pore-uniform frameworks in these membranes permit fast permeation of organic liquids with a notable molecular weight cutoff of 388 g mol−1 in ethanol. To demonstrate scalability, we show that our strategy can produce large-size COP membranes with a prominent area of 200 cm2, which exhibit performances similar to that of small membrane coupons. The present study offers a potentially scalable method for producing highly microporous COP membranes toward efficient molecular separation in organic liquids. [Display omitted] • A three-dimensional COP with uniform and subnanometer pores is synthesized. • Ultrathin COP membranes are rapidly prepared at ambient conditions. • The optimal COP membrane shows high selectivities with decent solvent permeances. • We produce large-size COP membranes without losing their separation performance. [ABSTRACT FROM AUTHOR]

Membranes with permselective performance as well as high stability in harsh solvents are urgently desired for energy-efficient precise chemical separations. In this work, we utilize an adamantane diamine as a molecular building block to fabricate thin-film composite polyamide membranes for high-performance organic solvent nanofiltration (OSN). The bulky, cage-like adamantane structure acts as a molecular-level steric hindrance unit to inhibit polymer chain packing which generating interconnected micropores within the interfacially polymerized polyamide layer. This translates into high membrane methanol permeance of 20.6 L m-2 h-1 bar-1 and 94.7% retention to organic dye molecules with molecular weight down to 327 g mol-1. Furthermore, the membrane demonstrates high stability in different organic solvents taking advantage of the crosslinked rigid structure, which shows constant solute retention throughout a 180 h continuous filtration experiment with a DMF solution containing methyl orange as feed solution. Employing rigid and bulky molecular features in selective layer is thus demonstrated to significantly promote the polyamide membrane permeability and solvent resistance without compromising the overall selectivity. [Display omitted] • A TFC OSN membrane was fabricated by using adamantane diamine as amine monomer. • The membrane is highly porous endowed by the specific geometry of adamantane. • The membrane shows a methanol permeance of 20.6 L m-2 h-1 bar-1 and MWCO down to ∼320 Da. • The membrane performs good resistance toward organic solvents. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) has been regarded as a promising membrane-based separation technology with great potential in many fields. In this work, based on the strong electrostatic interaction between nanoparticles (NPs) prepared by the quaternized P(VC- r -DMAEMA) (Q-PVD) and hydrolyzed polyacrylonitrile (HPAN) substrate membranes, separation nanochannels were successfully constructed on the surface of membranes by a one-step coating method. The types of the substrates and concentrations of NPs were optimized to obtain the proper performance. The surface morphology, chemical compositions, surface wettability, surface charge, and pore size were characterized. The obtained thin-film nanocomposite (TFN) membranes exhibited excellent stability in various common organic solvents, such as n -heptane, acetonitrile, ethanol, etc. Furthermore, composite membranes showed excellent retention for dyes with specific molecular weights, with a molecular weight cut-off (MWCO) of 825 Da. In particular, the rejection rates of Coomassie brilliant blue (BB) and Bengal rose red (RB) were 96.6% and 97.9%, respectively. Given the above characteristics, the composite membranes are expected to be used in the field of OSN. [Display omitted] • The amphiphilic copolymer nanoparticles were assembled to construct nanochannels. • The one-step coating method simplified the preparation procedure of OSN TFC membranes. • The membrane showed excellent separation capacity for dyes with specific molecular weights. • Further development of this technology is expected for tailor-made OSN membranes. [ABSTRACT FROM AUTHOR]

In this contribution, thin-film nanocomposite membranes with an interlayer (TFNi) were fabricated on poly (m-phenylene isophthalamide) (PMIA) substrates for organic solvent nanofiltration (OSN). The selective layer was formed by interfacial polymerization between 1,3,5-benzenetricarbonyl trichloride in the ionic liquid phase and mixed amine monomers in the aqueous phase. Five types of interlayer materials were prepared via a facile mixing method. After systematical characterizations, it was found that interlayer materials could not only adjust the surface morphology, porosity, and hydrophilicity of the substrate but also promote the controlled growth of thin and defect-free polyamide (PA) layer via the subsequent interfacial polymerization process. We also analyzed the radar chart representation of the various characteristic values of the membrane physiochemical properties (thickness, crosslinking degree, roughness, and hydrophilicity) and membrane separation performance (permeance, and rejection), in order to elucidate their relationships. Among the five TFNi membranes, PMIA/Co-PIP/PA membrane showed high ethanol permeance (2.93 L m−2 h−1 bar−1), high rejection (∼95%) of organic solutes with molecular weights above 697 Da, and robust long-term stability during separating erythromycin/methanol mixtures (50 h). The designed TFNi membranes were superior to the traditional PMIA/PA membrane, and the permeance of which was only 0.7 L m−2 h−1 bar−1. In addition, compared with the traditional PMIA/PA, the introduction of Co-PIP nanomaterials as an interlayer enhanced the tensile strength at break (12 vs. 19 MPa) and elongation of the PMIA/Co-PIP/PA membrane (32.0% vs. 83.9%). Accordingly, the designed PMIA/Co-PIP/PA membrane has great potential in industrial separation applications for drug concentration and organic solvent recovery. [Display omitted] • Nanomaterial interlayers were used to fabricate thin-film nanocomposite membranes. • Permeance of TFNi membranes was remarkably increased without sacrificing rejection. • The introduction of interlayers enhanced the mechanical property of the membranes. • Membrane physiochemical properties greatly affect the OSN separation performance. • Mixed amines were used as aqueous monomers for the interfacial polymerization. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is a membrane-based organic solution separation process that has emerged as a viable alternative to energy- and solvent-intensive separation processes. Polymers of intrinsic microporosity (PIMs) are the targets of recent active research on OSN membrane materials because of their unique physicochemical properties, such as solution processability, chemical tunability, robust porosity, and high thermal stability. However, applying PIMs-based membranes in practical OSN applications is still challenging because of their limited organic solvent stability and inevitable decrease in performance. Meanwhile, despite the potential of thin-film composite hollow fiber membranes for OSN, only a few studies have been reported to date. In this study, we fabricated a PIMs-based thin-film composite hollow fiber membrane by dip-coating and improved its organic solvent stability by intermolecular cross-linking. The membrane exhibited pure ethanol permeance of 10.9 LMH/bar and a molecular weight cut-off of 952 g/mol in ethanol. The membrane displayed stable dye rejection performance (>95%) even after immersion in ethanol, acetone, and toluene for seven days. This study demonstrates that intermolecular cross-linking between PIMs polymer chains can improve the organic solvent stability of PIMs-based membranes and provides a desirable strategy to fabricate feasible organic solvent stable PIMs-based thin-film composite hollow fiber membranes for OSN applications. [Display omitted] • An intermolecular cross-linked PIM-1 (XPIM) TFC hollow fiber (HF) membrane was developed for OSN. • The XPIM TFC HF membrane exhibited remarkable organic solvent filtration performance. • The XPIM TFC HF membrane showed stable rejection performance after immersion in organic solvents for seven days. • Intermolecular cross-linking can improve the organic solvent stability of PIMs-based membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A polyimide aerogel was applied as a versatile support for TFC and COF nanofiltration membranes. • Solvents and temperature affected the performance of the COF@aerogel membrane. • The pore flow model described the separation performance of the COF@aerogel membrane. • Stable performance was achieved under continuous, crossflow filtration for more than 9 days. • The polyimide aerogel support exhibited superior solvent resistance up to 6 months. Organic solvent nanofiltration (OSN) membranes require robust selective layers and support materials. In this study, polyamide and polyester thin-film composites (TFCs) and covalent organic frameworks (COFs) were fabricated as selective layers on a polyimide aerogel support. The ultrapermeable support was stable in various organic solvents including harsh polar aprotic solvents such as N , N -dimethylformamide (DMF), dimethylsulfoxide, N , N -dimethylacetamide, and N -methyl-2-pyrrolidone for more than six months. The support enabled fabricating both amorphous and crystalline selective layers at both room and higher temperatures. Moreover, the polyimide aerogel support had 85% porosity, facilitating high solvent flux. The compatibility of the selective layers and support was excellent, and as low molecular weight cutoff values (MWCO) as 356 and as high as 591 g mol−1 were obtained in methanol at 10 bar for the COFs and polyester TFC membranes, respectively. Both experimental MWCO and permeance values of the COF membrane agreed with those predicted using the pore flow model. The effect of the operating temperature on the OSN performance was examined in DMF at 20 and 100 °C. Both membranes demonstrated constant permeance and rejection for more than nine days of continuous filtration. [ABSTRACT FROM AUTHOR]

In this research paper we report two ways of controlling the molecular weight cut-off (MWCO) of PEEK membranes prepared via phase inversion and subsequent drying. The two methods explored were the change of polymer concentration in the dope solution – 8 wt%, 10 wt% and 12 wt% – and the variation of solvent filling the pores prior to drying – e.g. water, methanol, acetone, tetrahydrofuran and n-heptane. The results show that it is possible to vary the MWCO from 295 g mol −1 to 1400 g mol −1 by varying these parameters. A statistical analysis based on a genetic algorithm showed that the Hansen solubility parameter, polarity and their interactions with molar volume were likely to be the most important parameters influencing the performance of PEEK membranes when drying from different solvents. In addition, the drying temperature also proved to have an effect on the membrane performance – the higher the temperature the higher the rejection and the lower the permeance. [ABSTRACT FROM AUTHOR]

The сoupled solution-diffusion model based on the Maxwell-Stefan theory was developed to describe the solute rejection from dilute nonelectrolyte solutions by polymeric membranes applied in organic solvent nanofiltration. In certain cases, the advanced equation for the solute rejection can be reduced to the familiar expressions of the solution-diffusion and the Spiegler-Kedem models. The model was verified by the experimental results on the dyes nanofiltration through poly(1-trimethylsilyl-1-propyne) and poly(4-methyl-2-pentyne) membranes. Two binary separating systems were considered: first, the dilute ethanol solutions of three dyes with virtually the same molecular weight, and second, the selected dye dissolved in three different solvents. In contrast to the solution-diffusion model, the proposed approach provides an accurate description of both positive and negative solute rejection as a function of the transmembrane pressure. The contribution from the coupled solute flux to the total solute flux was quantitatively estimated. It is shown that the coupled solute flux becomes predominant over the direct diffusion flux when the membrane Peclét number reached the values of 1–2. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile method of crosslinking polybenzimidazole membranes using KMnO 4. • Crosslinking is quick and performed under relatively green and mild conditions. • Membrane shows superior separation performance and solvent stability. • No significant change in the membrane with either polar or nonpolar solvents. • Applications in petrochemical and pharmaceutical industries. Herein, a facile method for crosslinking polybenzimidazole membranes applied in organic solvent nanofiltration (OSN) using an aqueous potassium permanganate (KMnO 4) solution is presented. The membranes were crosslinked under mild water-based conditions at room temperature for less than 4 h. The crosslinked polybenzimidazole OSN membrane exhibited superior separation performance and enhanced stability in various solvents, including dimethylformamide and N -methyl-2-pyrrolidone. The crosslinked membranes exhibited greater than 90% rejection rate for dyes with molecular weights in the range of 327 to 1017 Da, and they were compatible with various common organic solvents such as ethanol, isopropyl alcohol, acetone, and dimethylformamide. Furthermore, no significant change in the membrane performance was observed when polar and nonpolar solvents were used in filtration experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous covalent organic polymer (COP) selective layer was synthesised on polybenzimidazole (PBI) supports. • Positively charged composite membranes with high salt retentions. • Composite COP membranes demonstrated excellent solvent and pH stabilities. • COP is further crosslinked to reduce the molecular weight cut off (MWCO) Here we present the preparation of a novel positively charged covalent organic polymer (COP) based nanofiltration membrane. The porous COP selective layer grows on top of a polybenzimidazole (PBI) support from coupling reaction of 1,3,5-tris(bromomethyl)benzene and 4,4′−dipyridyl in alkaline conditions. Chemical and morphological analyses confirm the formation of a thin layer of COP (less than 50 nm), which is also evidenced by its high water permeance and salt retentions. Moreover, it is shown that COP membranes can form hydrogen bonds with HNO 3 , leading to a tighter membrane pore size that increases the NaCl retention from 46% to 75% without significantly losing its permeance. Further, the composite membranes demonstrated exceptional solvent and pH stabilities. The COP membranes showed a molecular weight cut off between 400 and 1000 g mol−1 together with pure solvent permeances of 0.91, 2.4, 3.3, 7.1 and 9.5 Lm−2h−1bar−1 toward dimethylformamide (DMF), ethanol, acetone, methanol an acetonitrile, respectively. The remarkable performance together with the stability in harsh environments make the newly developed COP membranes an attractive candidate for extreme nanofiltration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thin TiO 2 -ZrO 2 -DTBC composite membranes were fabricated. • Pore sizes and surface properties were controlled by changing the firing conditions. • Surface free energy was calculated to consider the membrane-solvent interactions. • Membrane-solvent interactions, viscosity, and solvent size affected the solvent permeance. TiO 2 -ZrO 2 -(3,5-di- tert -butylcatechol, DTBC) composite membranes were fabricated via the sol–gel method under four different firing conditions: 300 °C (N 2), 300 °C (Air), 350 °C (Air), and 500 °C (Air). The chemical structure of the DTBC originated organic material in the composite was controlled by setting the firing temperature. The average pore sizes of the membranes were 1.0–1.1 nm when fired at 300 °C, 1.4 nm at 350 °C, and 2.1 nm at 500 °C. The molecular weight cut-off of the membranes (in daltons) in water ranged from 480 to 535 when fired at 300 °C, 890 at 350 °C, and 1,680 at 500 °C, whose corresponding molecular diameter was in good agreement with the average pore size measured via nanopermporometery. Permeation tests of the organic solvents showed that the membrane-solvent interaction affected the permeation mechanism in addition to the solvent viscosity and the occupied area of the solvent molecules. The surface free energy difference between the membrane and the solvent expressed the interaction between the membrane and the solvent molecule. The proposed solvent permeation model was examined and showed better agreement with the experimental results compared with the model based on the solubility parameters of a solvent. The organic solvent permeation mechanism of the ceramic NF membrane was greatly affected by the membrane-solvent intermolecular interaction. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is a green, environmentally friendly and sustainable separation technology. High-performance OSN membranes are expected to play a critical role in the field of chemical separation involving organic solvents. However, traditional OSN membranes suffer from the constraints on perm-selectivity. Herein, we introduced macrocyclic molecules with intrinsic angstrom-size cavity, pillar[n]arene (P[n]a, n = 5, 6), as a novel aqueous monomer to react with trimesoyl chloride (TMC) to prepare highly perm-selective thin-film composite (TFC) OSN membranes through interfacial polymerization. The prepared TFC-P[n]a membranes exhibit ultra-thin selective layer thickness of sub-10 nm and possess permanent intrinsic microporous structure, which endows the membrane with high perm-selectivity. Especially, the TFC-P[6]a membrane exhibits a high methanol permeance (8.10 L m−2 h−1 bar−1) and a low molecular weight cut-off (MWCO) of 300 g mol−1. In addition, the prepared TFC-P[n]a membranes exhibit molecule sieving function and could discriminate molecules with similar molecular weights but different shapes. Our work provides an insight of material design for the preparation of next-generation high-performance organic solvent nanofiltration membranes. [Display omitted] • The OSN membranes were prepared via IP of macrocyclic molecules pillar[n]arene with trimesoyl chloride. • The molecular cavity of pillar[n]arene and its 3D structure provide extra channels for transportation of solvent molecules. • The TFC-P[n]a nanofilms have ultra-thin thickness of sub-10 nm. • The MWCO of the TFC-P[n]a composite membranes were as low as ≤ 300 g mol−1. [ABSTRACT FROM AUTHOR]

Ceramic membranes show advantageous behavior over polymeric membranes under harsh conditions including high pH, high temperature applications or applications involving organic solvents. However, in the range of organic solvent nanofiltration (OSN) the currently available membranes do just offer a molecular weight cut-off (MWCO) of 600 g/mol or above. Here, a new approach is presented to manufacture ceramic membranes with active layers of titanium dioxide/zirconium dioxide with integrated carbon on top of a tubular ceramic multi-layer support. Filtration tests of these membranes with polystyrene mixtures in THF reveal a MWCO of 350 g/mol, thus extending the range of possible nanofiltration applications. The paper also presents a new combination of characterization of the membranes with permporometry and filtration tests that demonstrate the importance of the supporting layers for the creation of a good nanofiltration membrane. [ABSTRACT FROM AUTHOR]

Synthetic interlayers with multiple functions and structural stability have a high potential to construct novel thin film composite (TFC) membranes with demanding permselective property for precise separations. Herein, a functional interlayer derived from the polyelectrolyte-based layer-by-layer (LBL) self-assembly is reported to prepare interlayer engineered organic solvent nanofiltration (OSN) membranes using β-cyclodextrin (β-CD) as a monomer via interfacial polymerization (IP) process. Compared to the interlayer-free OSN membrane, a smoother selective layer with higher crosslinking degree is obtained for our developed membranes, enabling an improved organic dye rejection (e.g. , 91.9% for methyl orange and 98.8% for brilliant blue R). Importantly, the LBL-aided β-CD nanofilm exhibits competitive permeances towards both polar (e.g. , methanol, 5.8 LMH/bar) and nonpolar solvents (e.g. , hexane, 7.0 LMH/bar). These performances can be attributed to the multiple roles of LBL-based interlayer as preventing the intrusion of selective layer and creating dual linkages (i.e. , amide and ester), along with tailoring the physicochemical properties of caped β-CD nanofilm. Besides, the newly developed OSN membrane can discriminate between dye molecules with similar molecular weights and same charge but different molecular configurations. Meanwhile, its good structural integrity and long-term stability are also demonstrated by the 7-day filtration test using tetracycline in methanol and β-carotene in hexane, respectively, as evidence of constant solute rejections (≥90%) during the entire filtration process. This work unravels the functions of LBL-based interlayer in enhancing the OSN performance, offering new insights into shaping the development of interlayer engineered OSN membranes for real-life applications. [Display omitted] • An interlayer derived from polyelectrolyte-based LBL is constructed for OSN application. • The multiple roles of LBL-based interlayer in tailoring β-CD nanofilm are investigated. • Interlayered membranes possess high permeances for both polar and nonpolar solvents. • Structural integrity and long-term stability are confirmed by a 7-day filtration test. [ABSTRACT FROM AUTHOR]

The present investigation considers the flux decline during concentration of ethanolic extracts from Sideritis ssp. L. by nanofiltration. Membranes Duramem with molecular weight cut-off (MWCO) 300 and 500 Da have been used. Two sets of nanofiltration experiments are performed: dead end filtration in a stirred cell and cross flow filtration in a 4 flat sheet membrane rig. Comparable fluxes and rejections are observed. The membrane behaviour with respect to the operation conditions: transmembrane pressure and feed concentration is studied. The effect of the latter is illustrated by experiments with different feed concentrations and permeate-to-feed ratios. The discussion is supported by rejections and mass balance calculations. In both modes flux decreased with concentration and the observed rejections remained constant. Better conditions for reduced flux decline and tendency to a steady value are obtained by cross-flow nanofiltration. Combined with the greater membrane area and feed volume used in these experiments, these results can be regarded as having potential for larger scale applications. [ABSTRACT FROM AUTHOR]

Abstract: The emerging field of organic solvent nanofiltration (OSN) opened up novel opportunities in fractionation and purification of polydisperse mixtures during the last decade. In this work we report about the application of OSN for the valorization of lignin as a renewable source of chemicals. Oxidation of lignin yields high-value monomeric chemicals including vanillin and methyl vanillate which have to be separated from the remaining mixture of high molecular weight reaction products. Five membranes from the , and series with a molecular weight cut-off (MWCO) in the range of 250–900gmol−1 were characterized concerning solvent flux of ethyl acetate and rejection of four model compounds. Afterwards, four of the membranes were employed in the separation of the lignin product mixture which has a weight average molecular weight of approximately 1150gmol−1. Retentate samples were analyzed concerning monomer content and remaining molecular weight distribution by gas chromatography/mass spectrometry (GC/MS) and size-exclusion chromatography (SEC). All four studied membranes proved to be very effective in separating monomeric products from the reaction mixture. The best results in terms of permeate flux and rejection of high molecular weight compounds were obtained with S380, which therefore turned out to be the most appropriate membrane for the desired separation step. [Copyright &y& Elsevier]

In this work the selectivity of crosslinked organic solvent stable PBI membranes is tuned by varying the molar ratio of two grafting agents: a long flexible polymer modifier (Elastamine RE-1-1000, 1000 g mol-1) and a small molecule modifier (2-methoxyethylamine, 75 g mol-1). Grafting exclusively with the long chain modifier provided a membrane with a molecular weight cut-off (MWCO) of 2000 g mol-1 in acetonitrile. Increasing the proportion of small molecule modifier in the grafting reaction capped the grafting sites in the membrane. This caused a decrease in the grafting density of the polymer modifier and allowed for the MWCO to be customised between 2000 g mol-1 and 20,000 g mol-1 in acetonitrile. High grafting densities underlie this control of performance, with up to 43% increase in the specific weight of the membrane during modification. This technique was scaled up to the manufacture of 5 m lengths of membrane that were incorporated into 1.8″ x 12" spiral wound modules, which showed performance consistent with the flat sheet membranes. [Display omitted] • Crosslinked polybenzimidazole (PBI) membranes have high stability in harsh solvents. • Graft modification allows for customisation of the rejection profile of PBI. • Graft modifier is present throughout the permeation pathways of the membrane. • The resulting membranes span from loose nanofiltration to tight ultrafiltration. • The membranes have consistent performance as flat sheets and spiral wound modules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crosslinked polydimethylsiloxane (PDMS) composite membranes were developed. • The influence of PDMS molecular weight on solvent separation was evaluated. • Various solvent mixtures containing hexane and alcohols were separated. • Low molecular weight PDMS membranes showed less swelling and higher selectivity. • Solvent permeation and separation were due to membrane swelling and solvent dissolution. • Interaction of alcohol and hexane with PDMS determined the separation coefficient. Membrane processes have proven to be energy-efficient technologies for separation of various substances, including organic solvents. In this study, crosslinked polydimethylsiloxane (PDMS) composite membranes were developed for organic solvent separation. Precursor solutions containing double-ended vinyl PDMS with four different molecular weights were spin-coated onto a polyethersulfone membrane substrate, and the crosslinking reaction was accelerated by heat treatment to produce PDMS composite membranes. The influence of the PDMS molecular weight and crosslinking on the membrane properties and performance was tested. It was shown that less swelling, more selective hexane absorption, and increased separation coefficient was observed with decreasing PDMS molecular weight. The trade-off relationship between the permeance and the separation coefficient was observed as the membranes prepared with lower molecular weights of PDMS showed lower permeability and higher separation coefficient. The separation coefficient showed a maximum value at a supplied ethanol concentration of 50 wt%. In addition, various solvent mixtures containing hexane and alcohols were used for organic solvent separation performance test using the PDMS composite membranes. A correlation was observed between the separation coefficient and the difference of χ parameters between alcohol/PDMS and hexane/PDMS. The mechanisms for solvent permeation and separation were discussed based on the interaction parameters, membrane swelling and solvent dissolution. The results of this study could be used as guidelines for the development of solvent-resistant PDMS composite membranes. [ABSTRACT FROM AUTHOR]

Abstract: Integrally skinned asymmetric membranes made from Lenzing P84 polyimide were prepared by immersion precipitation from a casting solution containing dimethylformamide (DMF) as the solvent and 1,4-dioxane (dioxane) as the co-solvent. The variation of the ratio between DMF and dioxane in the dope solution used for membrane formation provided control over the molecular weight cut-off curves of the resultant membranes. Coupling this methodology with chemical crosslinking provided excellent solvent stability, enabling application of the resulting family of organic solvent nanofiltration (OSN) membranes to separations in DMF. An analysis of the separation performance of the membranes using a two parameter pore flow model showed an increase in the mean pore size and standard deviation of pore size as the membranes became “looser” with higher concentrations of DMF in the dope solution. It was not possible to increase the mean pore size whilst maintaining the standard deviation of pore size constant. Nevertheless, this work demonstrates that a series of highly solvent stable membranes with controlled molecular weight cut-offs could be formed from a single polymer/immersion precipitation platform. [Copyright &y& Elsevier]

Abstract: This paper describes a method for the determination of the relationship between solute molecular weight and rejection, often referred to as the molecular weight cut off (MWCO) of the organic solvent nanofiltration (OSN) membranes. This method utilises a homologous series of styrene oligomers spanning the nanofiltration range (200–1000gmol−1). Good separation of the individual oligomers was achieved using liquid chromatography with a reverse phase C18 column. The good solubility of the styrene oligomers in many organic solvents makes cross comparison of membrane performance across these solvents possible. This method also allows the determination of the molecular weight at which a rejection of >99.9% occurs in different solvents, making it a useful tool to test membrane and equipment integrity. [Copyright &y& Elsevier]

Crosslinking of polymeric membranes induces changes in both membrane stability and separation performance. Numerous membrane-crosslinking methods have been developed with the objective of obtaining improved membranes. However, none of these methods systemically investigated the stereochemical effects of the crosslinker in the pursuit of better stability and performance. Herein, we address this knowledge gap by presenting a systematic investigation of the stereochemistry of crosslinkers. The intrinsically microporous poly(ether-ether-ketone)-containing Tröger's base (iPEEK-TB) was synthesized and employed in the fabrication of organic solvent nanofiltration (OSN) membranes. Crosslinkers were carefully selected based on the stereochemical position of the two benzyl bromide functional groups, separated by distances of 4.3, 8.2, 8.5, and 12.4 Å and significant effects arising from crosslinking on membrane physical properties, morphology, and OSN performance were investigated. Crosslinked membranes showed excellent solvent resistance, mechanical flexibility, and thermal stability. As a function of crosslinking distance, the molecular weight cutoff (MWCO) values of the membranes varied in the range of 575–750 g mol−1. The para isomer of the crosslinkers resulted in higher permeance relative to membranes crosslinked with their counterpart ortho isomers, and vice versa , the ortho substitution resulted in higher solute rejection values compared with para isomers. An increase of 50% and 12% in acetonitrile permeance relative to the annealed benchmark membrane was observed upon the treatment using iPEEK-TB with 4,4′-bis(bromomethyl)biphenyl (p -BBMBP) and 2,2′-bis(bromomethyl)-1,1′-biphenyl (o -BBMBP), respectively, whereas a permeance decrease of approximately 23% and 32% was noted upon treatment with α,α′-Dibromo- p -xylene (p -DBX) and α,α′-Dibromo- o -xylene (o -DBX), respectively. The corresponding MWCO changes were found to decrease for all crosslinked membranes within the range of 12%–40%. The crosslinked membranes demonstrated stable performance in polar aprotic solvents such as N , N -dimethylformamide and N -methyl-2-pyrrolidone. The Molecular dynamic (MD) simulations supported the obtained performance results through the variations in the fractional free volume (FFV). This work demonstrates the importance of crosslinker selection for OSN membrane performance and solvent resistivity and opens new avenues for fine-tuning membrane stability and OSN performance. [Display omitted] • Crosslinking of intrinsically microporous poly(ether-ether-ketone) containing a Tröger's base unit. • Deconvolution of the thermal treatment effect from the chemical crosslinking effect. • Stereochemistry (ortho, para, size) affects the membrane separation performance. • Para crosslinker isomers exhibit higher permeance than their ortho counterparts. • The distance between two benzyl bromide groups in the crosslinker affects separation performance. [ABSTRACT FROM AUTHOR]

Anchoring flexible alkyl hydrophilic side chain domains into a rigid polymer structure promoted a high-performance organic solvent nanofiltration membrane. [Display omitted] • Polystyrene derivatives with alkylcarboxyl and sulfonated side chains were synthesized. • The crosslinked membranes exhibit improved dimensional flexibility. • The crosslinked membranes displayed good solvent stability in polar protic solvents. • The crosslinked membranes exhibited high separation performance in OSN application. • The study offers the opportunity of manipulating the properties of OSN membranes. Polymeric membranes are more practicable to the cost-effective and energy-efficient solvent recovery and molecular separation in solvent mixtures, but the construction of structure-defined chemically stable as well as high permeance polymer membranes for organic solvent nanofiltration (OSN) applications is an important challenge. Herein, we designed and constructed crosslinked block copolystyrene membranes containing flexible alkylcarboxylated and alkylsufonated side chains for high-separation performance in organic media. The flexible side chains anchored on the all-carbon network render the membranes with good dimensional flexibility due to the rational manipulation of the intermolecular and intramolecular bonding interactions within the crosslinked structured polymer chains. Depending on the crosslinking degree, the resultant membranes exhibited outstanding stability in polar protic solvents, mild polar aprotic solvents (THF, acetonitrile and acetone) and nonpolar solvents. Specifically, the CPS-24% membrane with a cutoff of 380 g mol−1 showed good ethanol permeance of 4.16 L m−2 h−1 bar−1 and a high-efficient molecular separation (>96%) of a broad range of small molecular weight solutes (organic dye molecules, organic building blocks and antibiotics). The membrane also achieved molecular level selectivity of two molecules with a mass difference down to 141 g mol−1, which is attractive for molecular separation in the chemical and pharmaceutical industry. This work provides a promising strategy to improve selective solvent permeation and separation of organic molecules in OSN membranes by introducing flexible hydrophilic/hydrophobic side chain domains into the main backbone of rigid polymer structures. [ABSTRACT FROM AUTHOR]

Here, highly robust and tight PBI-based OSN membranes were developed by reinforcing the active layer with an ultrathin polydopamine (pDA) coating followed by the simultaneous co-crosslinking of the pDA-coated PBI membrane. Although the pDA layer thickness was just under 5 nm, the pDA layer can effectively improve the rejection properties of the pristine PBI membrane by reducing the overall pore size and filling the defects at the membrane surface. The chemical and physical changes clearly showed the effect of the ultrathin pDA layer and co-crosslinking on the membrane properties and separation performance. The modified PBI membranes showed the improved rejection property and excellent stability in various organic solvents, even in polar aprotic solvents. The co-crosslinked pDA-coated PBI membranes showed a very high rejection properties to low molecular weight solutes (97.6% for 236 Da styrene dimer and 99.9% for 308 Da PPG) with stable solvent permeance. Moreover, significantly improved solvent permeances were observed without a notable decrease in the rejection performance after the prefiltration of polar aprotic solvents. The results showed the effective separation performance enhancement of OSN membranes by ultrathin pDA coating and the potential applications of solvent purification, reuse and valuable chemical recovery in various fine chemical industries. [Display omitted] • The PBI OSN membranes were prepared and modified by pDA layer coating and crosslinking. • The pDA coating and crosslinking greatly improve the OSN membrane performance. • The polar aprotic solvent prefiltration significantly enhances the permeance of crosslinked membranes. • The modified membranes exhibited outstanding rejection properties to small solutes in organic solvents. [ABSTRACT FROM AUTHOR]

In this work, a new molecular layer-by-layer deposition (MLD) approach was demonstrated to tailor thin-film composite (TFC) membranes with ultrathin microporous polyamide (PA) films as separation layers used for organic solvent nanofiltration (OSN). The extrinsic and intrinsic microstructures of the crosslinked PA layers were synergistically tailored by the layer-by-layer reaction between rigid tri-amine monomer 1,3,5-tris(4-aminophenyl)benzene (TAPB) with trimesoyl chloride (TMC). The thickness of defect-free PA layers, which exhibited a homogeneous cross-sectional morphology, was decreased down to 26 nm by regulating the deposition cycles, which is advantageous to achieve high solvent permeability. Moreover, the generated PA layers displayed high microporosity (specific surface area up to 114 m2 g−1) due to the rigid polyphenyl tri-amine structure of TAPB monomer. These characteristics conferred upon the prepared TFC membranes with exceptional solvent permeabilities (5.5, 5.0, 14.6, and 39.8 L m−2 h−1 bar−1 for ethanol, dimethyl formamide, methanol, and acetonitrile, respectively) and high rejection (93.2%) towards methyl orange (327 Da of molecular weight), all of which are higher than those of the majority of state-of-the-art TFC membranes using PA or other newly porous materials (e.g., polyacrylates, polymers of intrinsic microporosity-1) as separation layers. Furthermore, the membranes showed excellent solvent and pressure resistance due to highly cross-linking network character. Given the noticeable advantages of this method, a new alternative for preparing high-performance TFC OSN membranes can be provided. [Display omitted] • Molecular layer-by-layer deposition was developed to prepare TFC OSN membranes. • A new rigid tri-amine monomer of 1,3,5-tris(4-aminophenyl)benzene was used. • Highly microporous and ultrathin polyamide film was prepared as separation layer. • TFC membranes showed superb solvent permeability and dye rejection performances. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is still a niche technology in the chemical industry due to time and money consuming process development, as organic solvents cause complex interactions between membrane, solvent, and solute. These interactions are not fully identified, and a fundamental understanding of mass transfer through OSN membranes is not established so far. Accordingly, mathematical models in OSN lack a general predictive capability. To overcome this problem, we aim to extend the current knowledge by a comprehensive experimental investigation of two polyimide membranes in combination with 17 solutes with molecular weights of 114–339 g/mol covering the range from nonpolar to polar, and five solvents with various properties. The results indicate solvent-dependent rejection phenomena that may be explained by a difference in the impact of solute properties on the rejection in dependency of the solvent. Based on these findings, three solvent-dependent solute sensitivity regions are derived similarly to previous results for PDMS membranes. The investigation of membrane–solvent interactions revealed an impact of the spatial distance in the 3D space of the total Hansen solubility parameter between solvent and membrane with a specific impact on membrane–solute sensitivity. These new findings contribute to a better understanding of transport phenomena and can serve as a new basis for predicting the separation performance in OSN. • Solvent-dependent solute sensitivity regions were identified. • Depending on the specific sensitivity region, different transport phenomena occur. • Solute properties determine solute transport when membrane-solvent affinity is low. [ABSTRACT FROM AUTHOR]

Surface engineering of polymeric membranes can induce subtle changes in membrane properties and enhance their performance. Numerous membrane surface modification methods have been developed to improve the material performance. However, these methods can be complex, thus limiting their practical applications. Herein, we present a simple method for fabricating membranes with honeycomb surfaces by controlling the polymer molecular weight (M w). Spirobisindane-based intrinsically microporous poly(ether-ether-ketone) (iPEEK-SBI) homopolymers with low and high M w s were synthesized and used to prepare organic solvent nanofiltration (OSN) membranes. The significant effects of polymer M w on its physical properties, membrane morphology, and OSN performance were systematically investigated. iPEEK showed excellent solution processability, high Brunauer–Emmett–Teller surface area, and remarkable thermal stability. Three mechanically flexible OSN membranes exhibiting honeycomb surfaces with different honeycomb cell sizes were prepared using iPEEK-SBI homopolymers with low M w s at concentrations of 27–39 wt% in N -methyl-2-pyrrolidone. By contrast, the use of iPEEK-SBI homopolymers with high M w s yielded membranes with flat surfaces. The M w cutoffs of the membranes were fine-tuned in the range of 408–772 g mol−1 by adjusting the dope solution concentration. Although the M w cutoffs were unaffected by polymer M w , the membranes derived from the polymer with low M w exhibited substantially higher solvent permeance (18%–26%) than that of the high M w membrane prepared at the same dope solution concentration. Stable performance was demonstrated over seven days of continuous cross-flow filtration and a six-month aging of the membranes. This work shows the importance of surface engineering for OSN membranes by adjusting polymer M w. These findings open a new avenue for fine-tuning the properties of OSN membranes. Image 1 • Membranes prepared using intrinsically microporous poly(ether-ether-ketone). • Polymer molecular weight affects physical properties and membrane morphology. • Flat vs. honeycomb membrane surfaces studied via computational fluid dynamics. • Dope solution concentration affects honeycomb structure and Feret diameter. • Honeycomb surface demonstrate high thermal stability and stable performance. [ABSTRACT FROM AUTHOR]

In this study, green bio-membranes were investigated. Alginate membranes were prepared by crosslinking of sodium alginate in calcium chloride aqueous solution. By fabricating membranes simply using three abundant cheap materials i.e. sodium alginate, salt and water, we have demonstrated membranes with acceptable performance for OSN with excellent chemical stability. Membranes prepared on three different polymeric supports (PAN, crosslinked PAN and Cellulose) showed similar performance. The alginate membranes were also spun coated on glass plate and laminated on alumina support. Great chemical stability was observed towards various solvents including dimethylformamide and dimethylsulfoxide. Characterization tests with FTIR, SEM, AFM and contact angle were carried out. Using same support, many parameters were explored such as the alginate concentration and the post treatment such as drying, crosslinking or precipitating in non-solvent. The range of the membranes permeance was 0.08–1.8 L/m2 h bar depending on conditions used. The nanofiltration experiments revealed a molecular weight cut off of about 1200 g/mol when tested with dyes such as Methyl Orange, Brilliant Blue and vitamin B12 in methanol. We initiated the preparation of fully green organic solvent nanofiltration membranes using green routes by preparing alginate selective layer on top of cellulose support. This study demonstrates that alginate membranes can be a promising candidate for green organic solvent nanofiltration. Image 1 • Nanofiltration membranes with selective crosslinked alginate biofilm were prepared on PAN or cellulose supports and tested for OSN. • DMF stable composite membranes were prepared of such crosslinked biofilms on crosslinked PAN supports. • Freestanding biofilms of alginates were prepared and mounted on porous alumina and non-woven polyester and tested for DMSO and DMF. • The membranes were resistant to harsh organic solvents and had a molecular weight cut-off of 1200 g/mol. • The entire fabrication is green, from a biopolymer dissolved at room temperature in water to crosslinking in salt/water solution. • The prepared membranes are marked as a promising beginning of green OSN. [ABSTRACT FROM AUTHOR]

Synthetic membranes with a high selectivity for demanding molecular separations and high permeance have a large potential for the reduction of energy consumption in separation processes. Herein, for the first time, the fabrication of an ultrathin layered macrocycle membrane for molecular separation in organic solvent nanofiltration using per‐6‐amino‐β‐cyclodextrin as a monomer for membrane manufacturing by interfacial polymerization is reported. Compared to a regular nonfunctionalized cyclodextrin, a higher reactivity is observed, enabling a very fast membrane formation under mild conditions. The formed membrane is composed of a layered structure of polymerized cyclodextrin, which shows high stability in different organic solvents. The membrane exhibits excellent separation performance for organic solvent nanofiltration, both with nonpolar and polar solvents. Most importantly, this new membrane type can discriminate between molecules with nearly identical molecular weights but different shapes. The unmatched high permeance and shape selectivity of the membranes can be attributed to the ultralow thickness, controlled microporosity, as well as the layered macrocycle structure, which makes the membranes promising for high‐performance molecular separation in the chemical and biochemistry industry. [ABSTRACT FROM AUTHOR]