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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]

[Display omitted] • Three new poly(ether-ether-ketone) copolymers with backbones having sulfonyl moieties were synthesized. • The monomer ratio for copolymerization varied between 0.25 and 0.75 for CH 3 and SO 2 containing monomers. • PEEK-based solvent-resistant membranes were prepared using TamiSolve via phase inversion and crosslinking. • Correlation between the copolymer composition, dope solution and membrane performance were established. • Molecular dynamics revealed the interactions between polymers and solvents. Poly(ether-ether-ketone) (PEEK) is an attractive material for membrane fabrication due to its exceptional thermal and chemical stability. However, traditional PEEK processing necessitates the use of harsh chemicals, such as sulfuric acid because of its limited solubility in organic solvents. To overcome this limitation, copolymers offer a solution by enhancing solubility and subsequently improving membrane characteristics such as permeability and selectivity. Herein, three novel copolymers – PEEK with various contents of SO 2 and CH 3 – were developed and used in membranes for the separation of polar and non-polar solvents. The chemical structure of the copolymers was tailored by varying the monomer ratio between 0.25 and 0.75 for CH 3 and SO 2 containing monomers. Diamine–crosslinked PEEK copolymer membranes were prepared using a green solvent (TamiSolve). The effects of the polymer structure, the dope solution rheology, and membrane properties together with separation performance were studied. The resulting membranes demonstrated a permeance for acetonitrile ranging from 7.4 to 8.2 L m−2 h−1 bar−1 with molecular weight cutoffs of 839–915 g mol−1. Molecular dynamic simulations were conducted to explore the interaction between the copolymers and nine different organic solvents. Our findings underscore the significance of copolymer design in achieving tailored membrane properties for diverse separations. [ABSTRACT FROM AUTHOR]

Polyamide thin film composite (PA-TFC) membranes have shown great potential in organic solvent separations. However, the intrinsic polar feature of the amide group limits their permeability to specific solvents, such as nonpolar solvents. In this study, we used a fluorine-containing monomer [4,4′-oxybis(3-(trifluoromethyl)aniline), OTFA] to conduct interfacial polymerization (IP) with trimesoyl chloride, resulting in the fabrication of novel PA-TFC membranes with permeability to both polar and nonpolar solvents. Interestingly, by simply adjusting the composition of OTFA solvents [DMF and DMF/water (1:1, v: v)], we obtained two PA-TFC membranes (OTFA-D and OTFA-DH, respectively) featuring completely different structures and surface properties, including PA layer thickness, water contact angle, surface element composition, surface charge, and polarity. Due to their distinct structures and surface features, the two membranes exhibited different performances in organic solvent nanofiltration (OSN). The OTFA-DH membrane showed higher permeability to polar solvents (e.g., methanol), while the OTFA-D membrane was more permeable to nonpolar solvents (e.g., toluene). The mechanism on the formation of the two PA layers was clarified by combining the experimental results with the molecular dynamics simulations. The significantly different interfacial properties and monomer diffusion during IP led to the substantial differences in the formation of the PA network. This work provides a strategy to fabricate tailored PA-TFC membranes for various OSN scenarios by simply adjusting the solvent compositions. [Display omitted] • First use of 4,4′-oxybis(3-(trifluoromethyl)aniline (OTFA) for polyamide formation. • N,N-dimethylformamide (DMF) and DMF/H 2 O (1:1) were used as OTFA solvents. • Membrane prepared with DMF/H 2 O (1:1) mixture was more permeable to polar solvents. • Membrane prepared with pure DMF was more permeable to nonpolar solvents. • Molecular dynamics simulations revealed OTFA solvent influenced monomer diffusion. [ABSTRACT FROM AUTHOR]

[Display omitted] • The unitary and binary pore CTF membranes were prepared by interfacial polymerization. • Ultrafast molecular-level perm-selectivity was finely tuned by the structural pore size. • The OSN membrane fouling could be alleviated via photocatalysis. • The membrane achieves multiple-cycle "operation-fouling-in situ cleaning-operation" stability for OSN process. Covalent organic frameworks (COF) membranes are considered as promising candidates for organic solvent nanofiltration (OSN) due to their well-defined porosity, high perm-selectivity, and exceptional resistance to solvents. However, irreversible membrane fouling caused by filter cake layers or pore clogging challenges the robust separation over long-term operation especially for well-known COF membranes. Here, we present novel ultrafast covalent triazine frameworks (CTF) membranes with retrievable separation performances for OSN processes. CTF-1 membrane with unitary nanopore and CTF-m membrane with binary nanopore are fabricated via an air-organic solvent interfacial polymerization technique for comparison, which demonstrates molecular-level selectivity (MWCO, ∼320 Da for CTF-1 and ∼ 625 Da for CTF-m) and ultrafast permeability for polar organic solvents. Moreover, the heterogeneous skeleton nanopores structure of CTF-m membranes facilitates efficient separation of photogenerated carriers, thus resulting in retrievable permselectivity. This work offers an efficient strategy via Donor-Acceptor structure modulation to tackle OSN membrane fouling, paving the way for applications of framework membranes. [ABSTRACT FROM AUTHOR]

• The compacted sponge-like structure was obtained via adjusting additive ratio. • The optimum cross-linker was screened to improve the stability. • High permeability was achieved via adjusting the coating conditions. • The LF-NMR technique was utilized to assess the affinity and stability. Purification and recovery of polar organic solvents such as dimethylformamide (DMF) with high chemical separation speed and low energy cost nanofiltration membranes has been widely investigated, while it is still a difficult challenge that high permeability of solvents and rejection of solutes are achieved simultaneously. In this study, a novel organic solvent nanofiltration (OSN) membranes was obtained via coating a thin selective graphene oxide (GO) layer on top of the polyimide porous substrate (PI) which was cross-linked to improve the stability in polar solvents. The resultant GO/cross-linked PI (GO/CLPI) composite membranes feature remarkable sieving capability of >94% for RBss molecules (1018 Da), accompanying high pure solvent permeability of 11.1 L h−1 m−2 bar−1, 4.9 L h−1 m−2 bar−1 and 1.0 L h−1 m−2 bar−1 for water, IPA and DMF, respectively. Different from conventional method of characterization, low field nuclear magnetic resonance technology (LF-NMR) was utilized to confirm that the GO/CLPI membrane shows a higher adsorption capacity for IPA than DMF. This newly technique can be effectively utilized to evaluate the affinity between organic solvents and the surface of membranes. [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]

Organic solvent nanofiltration (OSN) is a new type of organic fluid separation technology that can greatly reduce energy consumption compared with traditional distillation techniques. However, the development and application of OSN are restricted by the high manufacturing cost of solvent resistant membranes, including expensive materials and complex post-treatment process. In this paper, a low-cost polyaryletherketone bearing amino group synthesized from industrial raw material phenolphthalein was proposed, and then the crosslinked polyaryletherketone membrane with remarkable stability in polar aprotic solvent was prepared by green, mild and simple crosslinking method. The separation accuracy of the membrane can be easily adjusted from ultrafiltration to nanofiltration by altering the composition of the cast solution. In addition, the prepared membrane can be operated in DMF for 120 h, which indicated the excellent stability of the membrane, even for hash polar aprotic solvents. Therefore, this work demonstrates a novel low-cost solvent resistant membrane material that is promising for OSN applications. Schematic diagram of the preparation process of crosslinked PEK-NH 2 membranes. [Display omitted] • A novel low-cost polymer membrane material with good comprehensive performance. • Crosslinking occurs in aqueous solutions, which is a green, mild, and simple process. • The separation accuracy of the membrane can be easily adjusted from ultrafiltration to nanofiltration. • The crosslinked membranes exhibited excellent stability in common organic solvents including DMF. [ABSTRACT FROM AUTHOR]

Increasing concerns associated with the environment and global warming have triggered the exploration of the preparation of greener membranes. The abundance of renewable cellulosic biomass offers an excellent source material for membrane fabrication. In particular, cellulose acetate (CA) has been widely used as a membrane material. In this study, we explore the effect of the degree of acetylation (DoA) on membrane performance in organic solvents for the first time. We prepared CA membranes using nonsolvent-induced phase separation with Cyrene as a green solvent. Deacetylation was directly performed on the CA membranes to obtain a final DoA in the range of 1.2%–39.3%. The solvent resistance of the membranes increased as the DoA decreased. The membranes exhibited constant permeance at a pressure of 30 bar, which suggested the absence of compaction. Increasing the DoA increased the permeance of the polar aprotic solvents, whereas the permeance of the polar protic solvents showed the opposite trend. The hydrophilicity of the membranes increased with a decrease in the DoA, whereas the glass transition temperature remained quasi-constant and excellent thermal stability was maintained. The separation performance was fine-tuned with a molecular weight cut-off that ranged from 325 to 950 g mol−1 as a function of the DoA. Our results offer new avenues for tailoring solvent-resistant membrane materials from renewable polymers and solvents for application in harsh organic media. [Display omitted] • Cyrene was used as a green solvent to dissolve cellulose acetate and fabricate membranes. • Higher deacetylation degree resulted in membranes with higher solvent resistance. • Membranes with a degree of acetylation lower than 20% are stable in polar aprotic solvents. • The deacetylation retained the mechanical stability & enhanced the thermal stability of membranes. • The MWCO of deacetylated membranes ranged from 325 to 735 g mol−1 in polar aprotic solvents. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) offers an energy-efficient alternative to conventional thermal distillation processes for organic solvent separations. However, the fabrication of polymeric OSN membranes with adequate chemical stability in strong polar aprotic solvents remains a remarkable challenge. In this work, chemically robust polyamide thin-film composite (TFC) OSN membranes were fabricated by utilizing an innovative chemical modification of polyimide (PI) nanofiber substrate via one-step crosslinking and thermal cyclodehydration of terephthalic hydrazide (TPDH). The crosslinking and cyclodehydration reaction mechanisms were thoroughly elucidated and the effects of TPDH loading and thermal treatment conditions on solvent resistance and pore structure of the resulting TPDH/PI nanofiber substrates as well as the formation of the polyamide selective layer were systematically studied. The resulting TFC membranes show excellent stability in polar aprotic solvents (i.e., DMF, DMAC, and NMP), and a high DMF permeance of 9.4 L m−2 h−1 bar−1 was achieved with a 99.8% rejection to Rose Bengal at 2.0 bar. The outstanding long-term performance stability revealed the robust structure of the developed TFC OSN membranes. This work demonstrates a facile strategy to address the chemical stability limitations of TFC OSN membranes through a multifaceted yet generalizable approach of chemical crosslinking and thermal cyclodehydration. We believe this strategy can be broadly applied to different substrates, enabling TFC membranes to address a wide variety of unmet OSN needs. (TFC membranes with chemically robust TPDH/PI nanofiber substrates for polar solvent filtration). [Display omitted] • Polyimide (PI) nanofiber substrate was chemically crosslinked by terephthalic dihydrazide (TPDH). • Thermal cyclodehydration further improves the chemical robustness of the crosslinked TPDH/PI nanofiber substrates. • The modified TPDH/PI nanofiber substrates show outstanding stability in polar aprotic solvents. • The resulting polyamide TFC membranes exhibit excellent performance in organic solvent filtration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic solvent nanofiltration is a promising method for dendrimer purification. • Tight regenerated cellulose membranes are applicable in a range of organic solvents. • Effective pore size of cellulose membranes can be fine-tuned by solvent polarity. • Permeability of small solutes is affected more by their polarity than by their size. • Model assuming constant transmission shows a good agreement with experimental data. The performance of commercial cellulose membranes with pore size on the border between ultra- and nanofiltration in selected organic solvents was studied focusing on rejection of small solutes and applicability for dendrimer purification. Organic markers in the MW range 100 – 700 Da and polarity range from nonpolar to polar protic compounds (aliphatics, aromatics, ethers, esters and alcohols) were used for membrane characterization. Transmission experiments in mixtures of methanol and dichloromethane of variable ratio showed the suitability of tested membranes for intended purpose, bringing information on structural factors affecting the rejection. Besides solute molar volume, its polarity type, or affinity, most conveniently expressed by Hansen solubility parameters, was found to be a crucial factor; with increasing size of solute molecule the spatial arrangement becomes also important. Solvent composition influences not only the behavior of solutes, but it also affects the membrane structure: poor solvation of cellulose by less polar solvents causes partial pore collapse, resulting in a decrease of membrane molecular weight cutoff. This effect can be used to improve the retention of a target product, as was shown for the first generation amphiphilic dendron. In addition, a simple mathematical model, allowing to estimate the course of nanofiltration and to optimize its conditions in a semicontinuous dead-end setup, is presented. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration is a promising and more sustainable alternative to classic separation processes in multiple industries; however, proposed materials for polymeric membranes with high solvent stability mostly utilize unique or expensive polymers, or are fabricated by complex methods. Herein, a facile method is presented to fabricate crosslinked polyethersulfone membranes with remarkable stability in halogenated and polar aprotic solvents. After preparing the membranes by the conventional non-solvent-induced phase inversion process, a multidentate aromatic amine embedded in the polysulfone underwent diazotization/dediazonization to effectively crosslink the polymer matrix. Membrane performance was easily adjusted from ultra-to nanofiltration via the polymer fraction. The performance of the crosslinked polyethersulfone nanofiltration is similar to the state-of-the-art solvent stable membranes. A weeklong filtration experiment in dimethylformamide and chloroform underlines the membranes' excellent stability. Overall, the range of solvent stability and state-of-the-art performance, combined with high accessibility and scalability, make the presented membranes an ideal platform material. [Display omitted] • Intricately crosslinked PES membranes are prepared via dediazonization • The crosslinked membranes have excellent stability in a wide range of solvents • Membrane performance is preserved even in halogenated and polar aprotic solvents • Selectivity is easily adjustable from the UF to NF range • The presented procedure has a high potential for scalable SRNF membrane manufacture [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]

[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] • Systematic investigation of dissolved gas on solvent flux. • Gas flux is correlated with gas solubility in the solvent. • Gas solubility needs to be considered for membrane testing and process design. The first step in quantifying the performance of organic solvent nanofiltration membranes are usually lab-scale experiments with respect to flux and rejection. The necessary pressurization of the feed is either realized mechanically by a high-pressure pump or by means of a pressurized inert gas. While the latter option is most frequently applied, the gas may dissolve in the feed mixture and permeate through the membrane, affecting the transport of the other components. This potential effect is commonly neglected, inherently assuming that the gas solubility is negligible. The current study provides a systematic experimental investigation and analysis of the impact of dissolved gases on solvent flux for a hydrophilic DuraMem membrane, with gas solubilities assessed through PC-SAFT. The results prove that a gas with low solubility has a negligible effect on the solvent flux. In contrast, an increasing gas solubility may result in significant gas flux through the membrane with a considerable effect on the solvent flux. Furthermore, the correlation of the solvent flux with the gas solubility in the feed mixture is strongly non-linear. Therefore, gas solubility is recommended to be critically evaluated when conducting OSN experiments, specifically considering the final application. In that context, the permeation of dissolved gas has to be actively accounted for in OSN experiments for gas–liquid systems. [ABSTRACT FROM AUTHOR]

Graphene oxide lamellar 2D membranes are widely researched for ion separation and molecular sieving in aqueous solution. Extension of the research of GO-based membranes for organic solvent nanofiltration has drawn much attention but is still in its infancy. The relatively low solvent permeability remains a difficult problem to overcome. Inspired by the shell of the Namib Desert beetle, a heterostructured lamellar membrane was prepared by incorporating MoS 2 quantum dots (MQDs) into the graphene oxide membrane. A dual-functional zone was formed, where hydrophilic areas exhibited excellent absorption performance for polar solvents and hydrophobic regions were propitious to the discharge of polar solvents when incorporating a moderate amount (10%) MQDs, denoted as GM-10 (nonpolar solvents presented the opposite performance). The synergistic effects of the dual-functional zone successfully improved the transport efficiency for various solvents, and the flux of various solvents for GM-10 was over three times higher than that of the pure GO membrane. Simultaneously, the composite biomimetic membrane showed excellent stability. This paper provides a novel strategy for constructing a heterostructured dual-functional zone for 2D lamellar membrane modification without the sacrifice of rejection, revealing the potential for further optimization of separation performance and membrane stability. [Display omitted] • The biomimetic membrane was prepared by adding MoS 2 quantum dots into graphene oxide membrane. • Heterostructured dual-functional zone was formed, enhancing the transport efficiency. • The membrane showed excellent balanced separation performance for various dye organic solvents. • The membrane showed high stability in harsh condition and long-term operation. [ABSTRACT FROM AUTHOR]

Solvent resistance is a crucial property for achieving organic solvent nanofiltration (OSN) membranes with good separation performance and long lifespan. Polybenzimidazole (PBI) has been widely used for OSN membrane fabrication owing to its excellent mechanical properties, thermal stability, and resistance in various organic solvents. However, pristine PBI membranes show unsatisfactory stability in polar aprotic solvents. To circumvent this issue, extensive research has been conducted on the covalent crosslinking of PBI membranes. Herein, to develop a more sustainable crosslinking strategy, difunctional organic acids — oxalic and squaric acids — were used for the reversible crosslinking of PBI membranes in water at room temperature, affording robust membranes with long-term stability in polar aprotic solvents. An analysis at the molecular level of the difunctional acid crosslinking system based on p K a values and binding energies was presented. The molecular weight cutoff and solvent flux of the PBI membranes crosslinked with oxalic and squaric acids were 779 and 844 g mol−1 and 153.9 and 139.7 L m−2 h−1 bar−1 in N , N -dimethylacetamide at 30 bar, respectively. The crosslinking was successfully reversed under basic conditions, allowing the recovery of the pristine PBI polymer. A sustainability assessment revealed the advantages of the proposed crosslinking system over conventional covalent crosslinking approaches. The solvent-resistant properties of polybenzimidazole membranes are enhanced using a crosslinking approach by employing oxalic and squaric acids as mild organic acid crosslinkers in water under ambient conditions. [Display omitted] • OSN membranes formed via mild organic acid crosslinking at ambient conditions in aqueous solutions. • Difunctional organic acids with p K a lower than 5.23 can crosslink polybenzimidazole (PBI) membrane. • Improved membrane stability in NMP, DMSO, DMAc, DMF polar aprotic solvents up to two weeks. • Less hazardous and more sustainable crosslinking approach for OSN membrane fabrication. • Membranes crosslinked with oxalic and squaric acids were recovered as pristine PBI. [ABSTRACT FROM AUTHOR]

Membranes with high permeance, excellent selectivity coupled with adequate solvent resistance are required for organic solvent nanofiltration (OSN) applications. But the "trade-off" relationship between the solvent resistance and permeance remains a critical challenge for polymeric-based thin film composite (TFC) membranes with necessary chemical crosslinking. Herein, a novel facile cyclization modification of polyacrylonitrile (PAN) nanofiber substrate is proposed by a simply thermal treatment and subsequent alkaline hydrolysis, and employed for the fabrication of TFC-OSN membrane for the first time in strong polar aprotic solvent systems. The reaction mechanism involved, solvent resistance and pore structure of PAN nanofiber substrate brought by the modification are investigated. TFC-OSN membrane supported by the modified PAN nanofiber substrate exhibits ultrahigh solvent permeance up to 13.3 L m−2 h−1 bar−1 coupled with a 99.7% rejection in rose bengal/DMF system and a good long-term stability. This study is therefore believed to provide useful guidelines for the development of next-generation OSN membranes. [Display omitted] • A facile cyclization modification of PAN with thermal and alkaline treatment is proposed. • Modified PAN nanofiber substrate shows enhanced resistance in strong polar aprotic solvents. • The substrate with high porosity shows superior pure solvent permeance. • TFC membrane exhibits superior OSN performance to most previous works. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic solvent nanofiltration membranes were prepared using 4,4ʹ-(hexafluoroisopropylidene)bis(benzoyl chloride) (HFBC). • Hydrophobic nanofiltration membranes exhibited high permeance for toluene and hexane. • The MWCO is 500–600 g mol−1, and the permeance is 10–60 L m–2h−1 bar−1. • The TFC membrane demonstrated stable long-term performance. Polyamide (PA) is highly effective as a selective layer in case of nanofiltration (NF) membranes, mainly for filtering water and other polar solvents. The incorporation of fluorinated monomers in a polyamide network is a novel strategy for obtaining membranes with enhanced permeability in case of nonpolar solvents. In this study, PA thin-film composite membranes were prepared by interfacially reacting trimesoyl chloride (TMC) and 4,4ʹ-(hexafluoroisopropylidene)bis(benzoyl chloride) (HFBC) in an organic phase with 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) in an aqueous phase in a single step. The resulting membrane obtained using HFBC exhibited a considerably increased nonpolar solvent flux and selectivity in the nanofiltration range. Thus, the hydrophobicity of the PA layer and its permeance are effectively enhanced because of the incorporation of the fluorinated monomer. Therefore, high-performance membranes can be obtained for nonpolar solvent separation in petroleum refineries and purification in the pharmaceutical industry. [ABSTRACT FROM AUTHOR]

A new strategy to synthesize integrally skinned polybenzimidazole (PBI) hollow fiber membranes for organic solvent nanofiltration (OSN) has been developed in this study by means of covalent modification with α,α′-dibromo- p -xylene (DBX) and then ionic impregnation with 4-sulfocalix [8]arene (SCA8). This double modification strategy endows the PBI hollow fiber membranes with synergistically enhanced chemical stability, mechanical strength and molecular sieving property. The modified PBI hollow fibers have a molecular weight cut-off (MWCO) of 217 Da and a narrow pore size distribution. In addition, the newly developed PBI hollow fiber membranes display a broad-spectrum of applications in various polar, nonpolar, and aprotic polar organic solvents. 1-inch PBI hollow fiber membrane modules are also fabricated to concentrate 10 wt% oil/acetone mixtures under 10 bar for 30 days, which provide an acetone permeance of around 0.35 L m−2 h−1 bar−1 and an oil rejection >99.5% after stabilization. This work may propose a feasible scheme to design OSN hollow fiber membranes and fabricate industrial-size modules with sharp molecular sieving capability to realize angstrom-scale separations in organic solvents. [Display omitted] • Integrally skinned PBI hollow fiber membrane without macrovoids is fabricated. • DBX covalent crosslinking constructs a mechanically and chemically stable PBI chain. • SCA8 ionic interaction enhances the molecular sieving capability of PBI membrane. • 1-inch PBI hollow fiber modules are fabricated for industrial separations. • Developed hollow fiber module exhibits structural integrity and chemical stability. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) nanomaterials have broad application prospects for the fabrication of separation membranes due to their high porosity, adjusted pore size, and excellent chemical stability. In this work, we in-situ constructed an ultra-thin layer of two-dimensional COFs nanomaterial using interfacial condensation between p -phenylenediamine and 1,3,5-triformylphloroglucinol, both with ultra-low concentration, on polyimide substrate surface to manipulate the subsequent interfacial polymerization between m -phenylenediamine of ultra-low concentration and trimesoyl chloride to fabricate a kind of thin film nanocomposite (TFN) membrane for organic solvent nanofiltration (OSN). The fabricated TFN OSN membrane achieves a Rhodamine B (479 Dalton) rejection and an ethanol permeance of higher than 99% and of 60 L m−2 h−1 MPa−1, respectively. Moreover, it has ultra-smooth surface with much thin skin layer, and high permeance for polar solvents such as methanol and ethanol. Besides, it has a molecular weight cut-off of about 375 Dalton. Moreover, it can maintain good separation performance after more than 10 days' immersion in N , N -dimethylformamide (DMF) at 80 °C, or after 120 h crossflow filtration with 100 mg L−1 Rose Bengal (1017 Dalton) - DMF solution as feed at 25 °C, indicating its vast potential for industrial application in harsh solvent environment. [Display omitted] • In-situ constructing nano-porous interlayer of two-dimensional COFs using Tp and Pa. • COFs interlayer effectively regulated the interfacial polymerization process. • COFs interlayer has profound effect on structure and performance of the OSN membrane. • The fabricated OSN membrane has ultra-smooth and ultra-thin barrier layer. • The fabricated OSN membrane has demonstrated superior solvent resistance. [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]

Advanced organic solvent nanofiltration (OSN) membranes with high permeance and stability are highly needed in petrochemical and pharmaceutical industries. Recently, polymers of intrinsic microporosity (PIMs) have attracted significant attention for the development of advanced membranes, because of their high porosity and solution processability. In this study, a thin film composite membrane based on an amidoxime-functionalized PIM (AOPIM-1) was prepared by spin coating followed by solvent activation. The activation approach could dramatically improve the solvent permeance of the membrane without compromising its rejection performance. The changes in porosity of the AOPIM-1 layer before and after activation were confirmed by positron annihilation Doppler spectroscopy. The optimum membrane exhibited an impressively high ethanol permeance of 15.5 L m−2 h−1 bar−1, nearly one orders of magnitude higher than that of Starmem240 (a commercial polyimide-based OSN membrane) with a comparable rejection of Rose Bengal (MW 1017 Da). In addition, the present membrane exhibited outstanding stability in polar solvents and a remarkably high rejection of active pharmaceutical ingredients (vitamin B12) from ethanol. This work could provide a new avenue for developing highly permeable OSN membranes and is expected to stimulate the use of PIM membranes in OSN applications. [Display omitted] • AOPIM-1thin film composite membrane was prepared by a facile spin-coating and solvent activation method. • Solvent activation could enhance the resultant membrane performance effectively. • The resultant membranes have better stability in polar solvents. • The resultant membrane shows ultrahigh solvent permeance and excellent rejection for Vitamin B12. [ABSTRACT FROM AUTHOR]

• Novel OSN membrane based on nanofibrous insoluble polyimide substrate. • Enhanced imidization degree and solvent stability. • Enhanced mechanical properties and promising membrane performance. Permselective thin-film composite membranes are gaining a significant role in solvent-based molecular sieving applications. Nevertheless, the lack of desirable substrate materials, which combines high flux, solvent resistance as well as a straightforward fabrication process, is still the biggest bottleneck for large-scale commercial implementation. For the first time, we propose to fabricate an insoluble polyimide nanofibrous substrate by a sequential strategy involving electrospinning polyamic acid followed by a thermal imidization. The water-absent electrospinning process leads to 1-fold enhanced mechanical strength and higher solvent-resistance of substrate compared to the conventional phase inversion process. The resultant thin-film nanofibrous composite (TFNC) membranes exhibit exceptional potential for nanofiltration by showing high permeability, rejection, and stability in water as well as polar aprotic solvents such as dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran compared to state-of-art membranes. The strategy of using electrospun insoluble polyimide as the substrate establishes a scalable approach to design high-performance TFNC membranes for a wide range of challenging molecular sieving applications. [ABSTRACT FROM AUTHOR]

• A TA-Cu complex interlayer was in-situ formed for the preparation of OSN membrane. • TA-Cu interlayer optimized interfacial properties of substrate. • The optimized OSN membrane has ultra-thin and ultra-smooth skin layer. • The interlayered TFC OSN membrane achieved excellent enhanced separation performance. • The TA-Cu interlayered OSN membrane exhibited satisfying long-term stability. In this work, a novel organic solvent nanofiltration (OSN) membrane was engineered precisely via interfacial polymerization on the surface of an interlayer which was in-situ constructed using tannic acid – copper (TA-Cu) complex on the surface of a polyimide substrate membrane, and then was followed by crosslinking and activation procedures. The most promising aspect of this work is the high separation and solvent permeation performances due to the ultrathin film obtained in the interfacial polymerization reaction using ultra-low concentration monomers, 0.025 wt% aqueous m-phenylenediamine (MPD) and 0.0050 wt% trimesoyl chloride (TMC) in organic solution, respectively The optimized interlayered thin film composite (TFC) OSN membrane achieved a rejection of 98.36% for Rose Bengal (RB, 1017 Da) and a DMF permeance of 150.05 L m−2h−1 MPa−1 for 100 mg L−1 RB-DMF solution, much higher than most of the state-of-the-art literature works. Furthermore, after a 75 h' filtration, it remained a 98.7% rejection for RB of the RB-DMF solution, proving a high resistance to strong polar solvent. Meanwhile, it has an average surface roughness of less than 4.5 nm, a thickness of about 15 nm for the PA skin layer. This OSN membrane fabrication strategy is much economical and much environmentally friendly, and shows great potential for the application in the separation of organic solvent systems. [ABSTRACT FROM AUTHOR]

• An ultrathin and stable organic-inorganic lamellar composite membrane was designed. • Precise control of membrane structure is realized by electrostatic atomization method. • High solvent permeance and precise molecule rejection are both guaranteed. • The membrane achieves excellent structure, operation, pressure, and cycling stabilities. Two-dimensional (2D) lamellar membranes hold a broad prospect for separation applications. However, their design and development need controllable fabrication of ultrathin and stable lamellar membranes. Here, an organic-inorganic lamellar composite membrane with layer-by-layer graphene oxide (GO) and polyethyleneimine (PEI) structure was fabricated through a dual-needle electrostatic atomization strategy. The GO nanosheets work as skeleton to ensure ultrathin and defect-free membrane structure, while PEI cross-links adjacent GO nanosheets for structure stability. Importantly, this membrane achieves fast polar solvent permeance: 46.2 and 146.8 L m−2 h−1 bar−1 for water and acetone, outperforming most reported GO-based membranes. Meanwhile, the ordered and cross-linked interlayer channels provide accurate size sieving for industrial dyes (larger than 1.6 nm) with the rejection of above 96%. Significantly, this lamellar composite membrane displays excellent structure, operation, pressure, and cycling stabilities, which are difficult for traditional lamellar membranes. [ABSTRACT FROM AUTHOR]

• GQDs were introduced in GO nanochannels to tune physicochemical microenvironment. • GQD@GO membrane yielded highly enhanced permeance for polar and nonpolar solvents. • GQD@GO membrane showed excellent rejection of 95% for dyes with size of 2.0 nm. • GQD@GO membrane also displayed outstanding structural stability. • This strategy is universal when taking PQD@RGO as an example. Lamellar membranes are promising for highly selective permeation, among which graphene-based ones are widely studied. However, graphene-based membranes give limited molecule permeance due to the unfavorable microenvironments of nanochannels, mainly single chemical affinity and narrow channel size. Herein, quantum dots (QDs) were introduced into nanochannels to manipulate the microenvironments for optimized performance. Particularly, hydrophobic graphene quantum dots were anchored in hydrophilic graphene oxide nanochannels to improve the affinity towards nonpolar molecules and locally enlarge the channel size from 0.84 to 1.35 nm. The pleasant affinity facilitates rapid dissolution and entry of molecules into nanochannels, and the enlarged channel size promotes their fast transport. This synergistic effect permits remarkably enhanced permeance for both polar and nonpolar molecules, especially for nonpolar ones. Meanwhile, the narrow distance at QD-free area effectively rejects dyes larger than 2.0 nm. Additionally, the strong covalent bonds between QDs and adjacent nanosheets bring superior stability for membranes. [ABSTRACT FROM AUTHOR]

• Polyamide TFC membranes were formed onto ceramic supports for testing in OSN. • Membranes were found to have irreversible changes in performance after exposure to solvents. • Membranes exhibited different selectivity in different solvents. • Charged dyes exhibited higher rejection than uncharged dyes. The polyamide thin film composite (TFC) has been the standard platform for reverse osmosis and nanofiltration membranes for aqueous separations for decades. It combines the properties of high permeance and unmatched selectivity for desalination applications. The highly cross-linked structure of polyamides may enable its use in organic solvent separations with several studies showing promising results. The field lacks, however, a complete understanding of how polyamides may be impacted by solvent exposure. To investigate the impacts of solvent on polyamide, we formed polyamide selective layers through interfacial polymerization onto ceramic UF supports. We quantified the permeability and selectivity changes after polyamides were exposed to an alcohol (methanol), and a ketone (acetone), and a polar aprotic solvent (DMF). We used aqueous testing before and after exposure to quantify permanent changes in membrane performance. Our results show that not only are the polyamide properties altered by the exposure to solvents, but they also show that different solvents have very different impacts on polyamide performance. The results indicate that polyamides may not be robust enough to perform nanofiltration separations in solvent environments with predictable permeability and selectivity. [ABSTRACT FROM AUTHOR]

Preparation of highly permeable and selective organic solvent nanofiltration (OSN) membranes is desired for precise chemical separations. Although the emerging nanomaterials and novel preparation methods have significantly boosted the membrane performance, it still requires much effort to drive them toward scale-up production with lower cost and easier preparation process. Herein, we constructed a polyarylate membrane from one kind of porous organic cage, namely Noria through traditional interfacial polymerization technique. Under the catalysis of triethylamine, Noria in aqueous phase would react with terephthaloyl chloride (TPC) in hexane to form a dense nano-film. The inner cavity of Noria molecule provided nano-channel for both polar and non-polar solvents to transport through the membrane. Specially, the Noria + TPC membrane exhibits a high permeance for methanol up to 18 L m−2h−1bar−1. This is resulted from the low interaction energy between methanol and Noria as revealed by the molecular dynamics (MD) simulation. In addition to the excellent performance, the simple preparation process with low-cost materials suggests the great potential of Noria + TPC membrane for practical application. Moreover, it would inspire the exploration of other molecules with tailored chemical structures for the assembly of high-performance membranes in future. Image 1 • The OSN membrane was synthesized via interfacial polymerization of a porous organic cage with acyl chloride. • The molecular cavity of Noria provided nano-channel for the transport of both polar and non-polar solvents. • The MD simulation revealed the mechanism for the high permeance of methanol. [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]