Achieving ultrahigh permeance and superoleophobicity is crucial for membrane application. Here, we demonstrated that a poly(ionic liquid)/PES hydrogel membrane can achieve dual goals. The high polarity of the ionic liquids induces the water molecules on the membrane surface to be arranged more ordered, as verified by molecular dynamics (MD) simulation and advanced femtosecond sum frequency generation (SFG) vibrational spectroscopy. Meanwhile, a large amount of water exists in membrane pores, demonstrated by water absorption, low-field nuclear magnetic resonance, and SFG spectroscopy. The interfacial water layer endows the membrane with superior anti-oil-fouling properties, and the large amount of water in membrane pores imparts membrane with ultrahigh permeability. The positive charge on the channel surface and moderate channel size confer a high rejection of metal ions. The optimal membrane exhibited a permeance of 35.1 L m-2 h-1 bar-1, 5-10 times that of conventional hydrogel membranes with similar rejection. Moreover, the membrane exhibited excellent antibacterial properties. It can be expected that highly polar poly(ionic liquid) membranes will find promising applications in the water treatment field.

Achieving strong interaction with the targeted composition and constructing abundant transport channels is crucial to obtain the pervaporation (PV) membrane with high selectivity and flux. Here, three ionic liquids (ILs) were screened out based on their relative selectivity and capacity targeting for bioethanol dehydration by COSMO-RS. The interaction energies analysis between ILs, EtOH, and H2O suggests that the ILs can form strong hydrogen bonds with water and disrupt the hydrogen bond in the EtOH-H2O azeotropic mixture, which is beneficial for improving the selectivity. Furthermore, driven by the multiple hydrogen bonds, electrostatic interactions, and van der Waals forces, ILs could self-assemble with polyvinyl alcohol (PVA) to fabricate the PV membrane with well-ordered micelle nanostructure, as its structure was revealed by MD simulations. The formation of the ILs-PVA micelle dramatically influenced membrane surface morphology, roughness, and water contact angle, providing an extra transport channel for the membrane. The optimal membrane (at the cmc point) exhibited a superior ethanol dehydration separation factor of 1627, along with a flux of 684 g/m2h at 50 degrees C. It can be expected that this novel self-assembled ILs-PVA micelle nanostructure strategy will find promising applications in other azeotropic mixture separation processes, like ethanol-ethyl acetate, water-butanol, etc.

Ionic liquids (ILs) have recently emerged as a new membrane material for efficient separation. In this review, current achievements of nanofiltration (NF) membranes modified by ILs are highlighted. ILs, comprising cations and anions, possess excellent tunability of functionalized groups, high polarity, high chargeability, good antimicrobial properties, low vapor pressure, and eco-friendly characteristics, which can enhance the hydrophilicity and chargeability of the NF membrane, provide additional water transport channels and water transport efficiency, as well as improve the ion selectivity, antifouling, and antibacterial properties of the NF membrane for green and sustainable separation process. Meanwhile, the challenges and future research interests toward the interaction behavior between ILs and targeted substance, the regulation of membrane surface interface properties, the separation mechanism, and the inadequacies of s-based NF membranes are discussed.

MOFs-modified nanofiltration (NF) membranes have been gained a lot of attention due to their favorable permeability and ion separation performance. Nevertheless, the prevailing preparation techniques are afflicted by the incompatibility of MOFs with polymers and the facile loss of MOFs. In this work, polyethyleneimine (PEI)-templated ZIF-8 (PEI-ZIF-8) was synthesized and incorporated into the PEI aqueous solution, then interfacial polymerized with trimesoyl chloride (TMC) to obtain the PEI-ZIF-8 modified polyamide NF membrane. This PEI modified strategy could endow the ZIF-8 nanoparticles with positively charged properties to avoid the aggregation and increase the interfacial compatibility with the polyamide. Meanwhile, the appropriate pore size of ZIF-8 (3.4 Å), which is between the hydration sheath surrounding of Li+ (2 Å) and Mg2+ (4.2 Å) impart the membrane with precise Mg2+/Li+ separation ability. The optimal PEI-ZIF-8-TMC membrane exhibits a permeance of 9 L/h m2bar and a Mg2+/Li+ separation factor (SF) of 19, both of which surpass the performance of the pure PEI-TMC membrane, which has a permeance of 4 L/h m2bar and a Mg2+/Li+ separation factor of 11. Meanwhile, the membrane exhibited excellent long-term stability of 85 h. This novel approach to preparing MOFs-modified NF membrane represents a promising avenue for the separation of lithium and magnesium.

Smart responsive nanofiltration (NF) membranes generated widespread interest for their ability to dynamically regulate permselectivity during operation according to the requirements of the separation. However, the reported smart membranes were usually impeded by limited stability as the problem of compatibility between conductive materials and a polymer membrane. Herein, we report a high-performance electrically responsive polyamide (PA) membrane for molecular NF by introducing an oligoaniline of amino-capped aniline trimer (AT) involved in the formation of a PA membrane. The membranes were prepared via interfacial polymerization (IP) of AT and trimesoyl chloride (TMC) on a porous substrate. The influence of AT, TMC, and dopant of the AT concentration on the membrane performance was systematically investigated. The results demonstrate that the introduction of AT significantly enhances the molecular separation performance of the membranes. The fabricated membranes exhibit excellent rejection toward small organic molecules while maintaining high water permeance and excellent long-term stability. Moreover, the membranes show remarkable electrocyclic responsiveness, allowing for effective control of the rejection rate by applying an external electric field. The improved performance of the membranes is attributed to the unique electrical and structural properties of AT doping by ionic liquids. Our findings provide valuable insights for the development of high-performance molecular nanofiltration membranes.

The conventional extraction of rare earth (RE) with alkali saponification consumes plenty of alkalis and produces enormous salt effluents. Herein, we propose a novel environmental-friendly non-saponified RE extraction process facilitated by acid-resistant nanofiltration (NF) membranes, in which the non-saponified organic phase directly extracts with RE feed by the multi-stage cross-current approach and the exchanged acid in the raffinate is removed by the acid-resistant NF membrane. The deacidified raffinate is reused as the feed of the non-saponified extraction. The obtained acid solution can be used for leaching or scrubbing after concentration. The feed concentration of the non-saponified extraction was optimized, and a high RE concentration of 0.21 mol L-1 in the organic phase and an average extraction rate of 89.9% were obtained with a 0.1 mol L-1 feed RE concentration. 99% of the acid in the raffinate was removed by acid-resistant NF under a RECl3 concentration of 4.9 g L-1, along with a recovered pH value of ~3, resulting in a high total RE yield of 99.6%. The acid-resistant NF facilitated non-saponified extraction featuring high atom economy, absence of alkalis consumption and salinity effluent emission, and eco-recycle of the raffinate render the separation of RE elements a versatilely sustainable and green process.

Superacid-catalyzed polymers of intrinsic microporosity have attracted increasing attention in membrane-mediated gas separation due to their good processability, facile polymerization procedure, and tunable microporosity and gas separation performance. In this study, we synthesized a series of new superacid-catalyzed polymers with fully ladder backbones and well-defined micropores using a one-pot condensation polymerization. The incorporation of a contorted spirobisindane building block facilitated the formation of highly microporous structures in the resulting polymers, enhancing their intrinsic microporosity and gas separation properties. Among the three SACPs, SACP-PhMe exhibited the largest d-spacing value, specific surface area, and pore volume due to its bulkiest side group. The gas separation performance of the SACP membranes surpassed several benchmark polymer membranes, with the SACP-PhMe membrane demonstrating excellent performance in separating CO2/CH4, H2/CH4, O2/N2, and H2/N2. The SACP-Me membrane exhibited the lowest porosity, making it less susceptible to CO2 absorption and showing superior plasticization resistance. The results highlight the promising gas separation properties of the SACPs and their potential for various gas separation applications, offering new opportunities for advanced polymer membrane design.

The fabrication of highly acid-resistant nanofiltration (NF) membranes with excellent separation performance via interfacial polymerization remains challenging due to the lack of precise pore architecture manipulation. Herein, novel acid-resistant nanofiltration membranes were fabricated based on benzene-1,3,5-trisulfonyl chloride (BTSC), which holds the characteristic resonant pi-backbonding structure and high steric hindrance, by interfacial polymerizing with polyethyleneimine (PEI) and piperazine (PIP) on the polyethersulfone (PES) substrate. The as-prepared PIP-BTSC/PES and PEI-BTSC/PES membranes displayed sub-nanometer pore sizes of 0.62 and 0.65 nm, respectively, with much narrower pore size distribution than the conventional acid-resistant NF membranes. Notably, the PEI-BTSC-H/PES membrane exhibited an MgCl2 rejection of 95.5 % and a high permeance of 43.5 L h-1 m- 2 bar-1. Besides, the PEI-BTSC/PES membrane exhibited excellent acid-resistance in the 72-day static acid soaking test and dynamic acid permeation experiment. Density functional theory calculation revealed that the outstanding acid-resistance of BTSC was ascribed to the much higher hydrolyzation energy barrier of the pol-ysulfonamide than conventional polyamide.

Highly permeable and selective synthetic polymer membranes are attractive for energy-efficient gas separations, while fabricating such membranes with well-defined micropore architecture and interconnectivity remains a significant challenge. We report the design and fabrication of highly crosslinked and microporous polymer nanofilms via engineering the bridged-bicyclic triptycene triamine moieties into the interfacially polymerized networks. The integrated polyamide nanofilms exhibited hierarchical pore structures with finely tuned microporosity (pore size 0.7-1.0 nm), ultramicroporosity (pore size 0.4-0.7 nm), and submicroporosity (pore size < 0.4 nm) and enhanced micropore interconnectivity due to triptycene-induced non-coplanar orientation and configurational free volume in the networks. Consequently, the composite membranes comprising polyamide nanofilms display exceptional gas separation performance for He and H2 recovery with enhanced permeances and selectivities as well as notable plasticization resistance compared to current state-of-the-art highly crosslinked TFC membranes. It is also proved that the microporosity and gas transport properties of the composite nanofilms are highly tailorable by regulating the reaction conditions. Incorporating hierarchical triptycene units with well-defined and interconnected microvoids provides the potential to fabricate highly permselective thinfilm composite membranes applicable for various important gas separations.

The conventional extraction of rare-earth (RE) elementsby alkalisaponification consumes plenty of alkalis and produces enormous amountsof salt effluents. Herein, we proposed a novel environmentally friendlynonsaponified RE extraction process facilitated by an acid-resistantnanofiltration (NF) membrane, in which the nonsaponified organic phasedirectly is extracted with the RE feed repeatedly by a multistagecross-current approach and the exchanged acid in the raffinate isremoved by the acid-resistant NF membrane with the deacidified raffinaterecycled for nonsaponified extraction. Using YCl3 as themodel sample, the feed RE concentration of the nonsaponified extractionwas optimized in the range of 0.1-1.0 mol L-1, and a high RE concentration of 0.21 mol L-1 inthe organic phase and an average extraction rate of 89.8% were obtainedafter seven-stage extraction at a RE feed concentration of 0.1 molL(-1). In total, 99% of the acid in the raffinatewas removed by the commercial Duracid NF1812 acid-resistant NF membraneunder an optimized RECl3 concentration of 4.9 g L-1, along with a recovered pH value of & SIM;3, resulting in a hightotal RE yield of 99.6%. The acid-resistant NF-facilitated nonsaponifiedextraction process featuring a high RE extraction rate and organicRE concentration, the absence of alkali consumption and salinity effluentemission, and eco-recycling of the raffinate renders the separationof RE elements a versatilely sustainable and green process.

Polytetrafluoroethylene (PTFE) with good resistance can be used under extreme conditions, however, its surface hydrophobicity greatly limits its wide application in water treatment field. In this work, the hydrophobic PTFE microfiltration (MF) membrane was innovatively modified into a hydrophilic loose nanofiltration (NF) via synergic effect of the deposited polyethyleneimine (PEI) and poly(vinylpyrrolidone) (PVP) with assistance of fluorocarbon surfactant (FCS), and then crosslinked by glutaraldehyde (GA). The surface morphology, porosity and aperture size of the obtained cPEI-PVP-FCS/PTFE (cPPF) membrane were characterized in detail. The resultant membrane showed good dye desalination performance with high Evans blue rejection of 98.5%, NaCl rejection of 13.4%, along with permeance of 192.1 L m(-2) h(-1)center dot MPa-1. In addition, the membrane showed longterm stability and good acid resistance.

Controlling the diffusion of amine monomers plays a crucial role in fabricating well-defined architecture and high-performance nanofiltration (NF) membranes through interfacial polymerization (IP). Herein, a sustained-release strategy was proposed to regulate the interfacial polymerization through a zwitterionic liquid hydrogel transition layer. The hydrogel (Gel) was fabricated via in-situ one-step UV photo-initiated free-radical poly-merization between 1-vinyl-3-ethylimidazolium chloride ([VEIm][Cl]) and 3-sulfopropyl methacrylate potas-sium salt (SMP) on the polyethersulfone (PES) substrate. The polyamide (PA) layer was then formed on the Gel layer by mitigating the diffusion of amine monomers. Low-field time-domain nuclear magnetic resonance (TD NMR) analysis demonstrated that the Gel layer significantly enhanced the water-absorbing capacity of the composite membrane. Positron annihilation lifetime spectroscopy (PALS) also confirmed the Gel-PA composite membrane possessed enlarged free volumes. The obtained Gel-PA composite membrane displayed a permeance of 13.22 L m- 2 h-1 bar-1, a high Na2SO4 rejection of 98.23 %, a favorable NaCl/Na2SO4 selectivity of 49.75, outstanding long-term operational stability, and membrane antifouling properties. This sustained-release strat-egy provides a facile and feasible approach to controlling the IP process and obtaining high-performance nanofiltration membranes.

This paper reports two new series of benzimidazole functionalized polyimides and ionic polyimides for highly selective membranes with great potential for natural gas sweetening. It has been demonstrated that both the -NH groups in the benzimidazole moieties and the corresponding ionic groups after N-quaternization tighten the microporous structure and restrict polymer chain mobility through hydrogen bonding and electrostatic interaction. The BET surface areas and d-spacing values decrease with benzimidazole molar content or the degree of ionization. Consequently, a linear correlation between CO2 permeability coefficients with benzimidazole molar content or degree of ionization was observed due to the decrease of CO2 diffusivity, and the monotonic increase of CO2/CH4 selectivities is ascribed to the increase of both diffusivity selectivity and solubility selectivity. The benzimidazole-based copolyimide and the ionic copolyimide membranes exhibited high CO2/CH4 selectivity under high-pressure mixed-gas conditions. In particular, the copolyimide PI-0.75 membrane displayed a mixed gas CO2 permeability of 27 Barrer and CO2/CH4 selectivity of 47 at 20 bar total pressure. The performance was much higher than those of the state-of-the-art commercial cellulose triacetate membranes for natural gas upgrading. The facile polymer synthesis and microporosity tunability, as well as the excellent mixed-gas separation performance, render the copolyimide membranes in this study promising towards economic membrane mediated natural gas upgrading.

The schematic diagram of interface interaction built by an IL between ZIF-7-8 nanoparticles and the polyimide matrix.

In order to enhance the permeance of the acid resistance membrane, an ionic liquid (IL) regulating strategy was proposed to rearrange the interfacial polymerization process. Herein, we revisited polyethylenimine (PEI) and cyanuric chloride (CC) as the pristine acid-resistant membrane. 1-aminopropyl-3-methylimidazolium chloride ([AEMIm][Cl]) and 1-aminopropyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([AEMIm] [Tf2N]) ILs were used to regulate the interfacial polymerization process. Molecular dynamic (MD) simulation was used to reveal IL and PEI diffusion behavior in aqueous solution, membrane pore size distribution, and porosity. The effects of ILs on membrane surface morphology, surface zeta potential, chemical composition, and separation property were analyzed. The IL regulating strategy endow the membrane with uniform smaller pore and higher porosity, thus improved membrane permeance and selectivity simultaneously. For the [AEMIm] [Cl] IL, the corresponding AEMIC-PEI-CC membrane showed high permeance of 79.1 L m(-2)h(-1)bar(-1), which is 1.36 times the pristine PEI-CC membrane, combined with high Y3+ rejection of 97.5%, low H+ rejection of 1.35%. In addition, this membrane showed good acid stability in 30 days long-term test.

Polymers of intrinsic microporosity have attracted comprehensive attention in membrane-mediated gas separation because of their rigid and contorted structure that facilitates well-defined microporosity for fast and selective gas transport. We report a new macromolecular design synthesizes semi-ladder and fully-ladder polymers of intrinsic microporosity containing 9H-xanthene units by superacid-catalyzed Friedel-Crafts polymerization named SACPs. The prepared SACP membranes display high microporosity with amorphous chain packing structure, high FFV, and high BET surfaces areas. In particular, SACP-3 exhibited the most elevated BET surfaces area of 568 m(2)/g, fractional free volume (FFV) of 0.243, and bimodal micropore size distribution with two maxima at similar to 5 and similar to 8 angstrom, respectively. Due to its fully ladder architecture, SACP-3 exhibits highly permeable gas transport with CO2 permeability of 6497 Barrer and CO2/CH4 selectivity of 7.8, respectively. The microporosity and gas permeation properties of SACP membranes are also demonstrated to be highly tailorable by employing different monomers. The facile polymerization procedure, excellent solubility and processability, highly diverse tunability, and outstanding gas separation performance render SACP membranes attractive for many membrane mediated gas separation processes.

The fabrication of nanofiltration (NF) membranes with excellent acid resistance and high separation performance remains a tremendous challenge due to the lack of precise membrane structure manipulation. Herein, covalent organic frameworks (COFs), due to their abundant porosity and highly ordered structures, are employed to synthesize high-permeation nanofiltration membranes. An acid-stable COF layer and a polysulfonamide (PSA) layer were fabricated by in-situ interfacial polymerization (IP) upon the polyethersulfone (PES) ultrafiltration substrate in turns. The acquired COF-based composite membrane exhibited sub-nanometer pore size and excellent rare-earth ions separation performance due to the interlaced stacking between the COF and PSA layers, as well as the COF interlayer regulated IP process. Additionally, the composite membrane showed high rejection of > 92.2% for trivalent rare-earth ions (RE3+) and high water permeance of > 43.3 L h-1 m(- 2) bar(-1) at both pH = 6.8 and pH = 1, the superior separation performance can be ascribed to the high porosity and abundant transportation pathway provided by the COF layer and the interlaced stacking structure between the COF layer and the PSA layer. The facile membrane fabrication procedure, along with the excellent water permeation performance and acid resistance, render the composite membrane in this study applicable for a broad range of critical industrial and environmental processes.

Designing and preparing nanofiltration (NF) membrane with distinguished property of acidic tolerance is attractive for handling acidic saline wastewater. In this work, we used a new monomer of 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoro-propane (bisAPAF) to prepare NF membrane by interfacial polymerization for removing dyes from acidic saline solution. Interestingly, the resulted NF membrane derived from bisAPAF and 1,3,5-trimesyol chloride (TMC) exhibits an exceptional structure stability under strong acid condition. Specifically, after exposed to H2SO4 aqueous solution with concentration of 20% (w/v) for 720 h, the NF maintains a Na2SO4 rejection of similar to 87%, showing little change as compared with the membrane without acidic treatment. In addition, the membrane shows a high selectivity for differentiating Direct Red 23/NaCl or Congo Red/NaCl in the pH range of 2-9, the rejection of dyes maintains at higher than 98% while the NaCl rejection is lower that similar to 10%. The outstanding acid tolerance property of NF membrane makes it a great promise candidate for acid wastewater remediation.

Improving the permeance of the polyamide (PA) membrane while maintaining the rejection is crucial for promoting the development of membrane separation technology in the practical water-treatment industry. Herein, a novel metal-ionic liquid (Zn-IL) coordination compound was synthesized by in situ growth to improve the water permeance of PA nanofiltration membranes, using an amine-functionalized IL (1-aminopropyl-3-methylimidazolium chloride, [AEMIm][Cl]) as a ligand to react with Zn(NO3)2·6H2O. Piperazine (PIP) and trimesoyl chloride (TMC) were adopted to prepare the PA layer covering the Zn-IL complex. Due to the unique property of the Zn-IL complex, the Zn-IL/PIP-TMC absorbing force to water was increased, enabling the fast transport of water molecules through the membrane pore channels in the form of free water. The resulting Zn-IL/PIP-TMC nanocomposite membrane exhibited a high permeance of up to 26.5 L m-2 h-1 bar-1, which is 3 times that of the PIP-TMC membrane (8.8 L m-2 h-1 bar-1), combined with rejection above 99% for dyes such as methyl blue.

Nanoparticle agglomeration in a polymer matrix is often an intractable issue for the advancement of nanohybrid membranes, and achieving scaled-up production also requires the development of simpler, more efficient and more environmentally friendly fabrication mechanisms than what are currently used. Herein, we report a hight-hroughput methodology for fabricating nanodisperse hybrid membranes by directly atomizing the oligomer (no solvent) and a crosslinker solution doped with nanoparticles and then allowing the nanoparticles to crosslink rapidly on a rotating substrate surface. It has been proven that a robust and defect-free nanohybrid membrane can be fabricated within 3 min, requiring almost 2-3 orders of magnitude less time than conventional solution-coating technologies (200-6700 min). Moreover, various nanoparticles can be dispersed uniformly on a nanometer scale into the selective layer by the atomization synergistic effect, and the resulting membranes exhibit excellent overall performance and good stability for biobutanol recovery. To further demonstrate the universality of this technique, this work has been successfully extended from flat-sheet substrates to hollow-fiber and tubular substrates. In addition, the environmental impact of nanohybrid membrane-making processes has been evaluated quantitatively to further illustrate the greenness of this facile approach.