Confined Nano-Channels Incorporated with Multi-Quaternized Cations for Highly Phosphoric Acid Retention HT-PEMs.

Developing a new strategy to retain phosphoric acid (PA) to improve the performance and durability of high-temperature proton exchange membrane fuel cell (HT-PEMFC) remains a challenge. Here, a strategy for ion-restricted catcher microstructure that incorporates PA-doped multi-quaternized poly(fluorene alkylene-co-biphenyl alkylene) (PFBA) bearing confined nanochannels is reported. Dynamic analysis reveals strong interaction between side chains and PA molecules, confirming that the microstructure can improve PA retention. The PFBA linked with triquaternary ammonium side chain (PFBA-tQA) shows the highest PA retention rate of 95%. Its H2/O2 fuel cell operates within 0.6% voltage decay at 160 °C/0% RH, and it also runs over 100 h at 100 °C/49% RH under external humidification. This combination of high PA retention, and chemical and dimensional stability fills a gap in the HT-PEMFC field, which requires strict moisture control at 90-120 °C to prevent acid leaching, simplifying the start-up procedure of HT-PEMFC without preheating.

Large-Area Soluble Covalent Organic Framework Oligomer Coating for Organic Solution Nanofiltration Membranes.

Covalent organic frameworks (COFs) are a family of engaging membrane materials for molecular separation, which remain challenging to fabricate in the form of thin-film composite membranes due to slow crystal growth and insoluble powder. Here, an additive approach is presented to construct COF-based thin-film composite membranes in 10 min via COF oligomer coating onto poly(ether ether ketone) (PEEK）ultrafiltration membranes. By the virtue of ultra-thin liquid phase and liquid-solid interface-confined assembly, the COF oligomers are fast stacked up and grow along the interface with the solvent evaporation. Benefiting from the low out-plane resistance of COFs, COF@PEEK composite membranes exhibit high solvent permeances in a negative correlation with solvent viscosity. The well-defined pore structures enable high molecular sieving ability (Mw = 300 g mol-1 ). Besides, the COF@PEEK composite membranes possess excellent mechanical integrities and steadily operate for over 150 h in the condition of high-pressure cross flow. This work not only exemplifies the high-efficiency and scale-up preparation of COF-based thin-film composite membranes but also provides a new strategy for COF membrane processing.

Phosphonated Ionomers of Intrinsic Microporosity with Partially Ordered Structure for High-Temperature Proton Exchange Membrane Fuel Cells.

High mass transport resistance within the catalyst layer is one of the major factors restricting the performance and low Pt loadings of proton exchange membrane fuel cells (PEMFCs). To resolve the issue, a novel partially ordered phosphonated ionomer (PIM-P) with both an intrinsic microporous structure and proton-conductive functionality was designed as the catalyst binder to improve the mass transport of electrodes. The rigid and contorted structure of PIM-P limits the free movement of the conformation and the efficient packing of polymer chains, resulting in the formation of a robust gas transmission channel. The phosphonated groups provide sites for stable proton conduction. In particular, by incorporating fluorinated and phosphonated groups strategically on the local side chains, an orderly stacking of molecular chains based on group assembly contributes to the construction of efficient mass transport pathways. The peak power density of the membrane electrode assembly with the PIM-P ionomer is 18-379% greater than that of those with commercial or porous catalyst binders at 160 °C under an H2/O2 condition. This study emphasizes the crucial role of ordered structure in the rapid conduction of polymers with intrinsic microporosity and provides a new idea for increasing mass transport at electrodes from the perspective of structural design instead of complex processes.

A Novel Material for High-Performance Li-O2 Battery Separator: Polyetherketone Nanofiber Membrane.

The properties of separators significantly affect the efficiency, stability, and safety of the lithium-based batteries. Therefore, the improvement of the separator material is critical. Polyetherketone (PEK) has excellent general properties, such as mechanical strength, chemical stability, and thermal stability. Thus, it is expected to be an optimal separator material. However, its low solubility-induced poor processibility makes it difficult to be used for nanoscale product manufacturing. In this work, the soluble precursor polymer is prepared by introducing a "protecting" group into monomer, and fabricated into nanofiber membrane, which can be converted into polyetherketone nanofiber membrane by a simple acid treatment. The membrane prepared by this chemical-induced crystallization method exhibits superior chemical, thermal stability, and mechanical strength. Li-O2 batteries with the fabricated membrane as separator have a high cycling stability (194 cycles at 200 mA g-1 and 500 mAh g-1 ). This work broadens the application field of PEK and provides a potential route for battery separators.

Nano-Interlayers Fabricated via Interfacial Azo-Coupling Polymerization: Effect of Pore Properties of Interlayers on Overall Performance of Thin-Film Composite for Nanofiltration.

The supporting layer of nanofiltration membranes is critical to the overall nanofiltration performance. However, conventional supports lack efficient surface porosity, which leads to the limited utilization rate of the polyamide (PA) layer. Herein a double-skin-layer nanofiltration membrane with porous organic polymer nanointerlayers prepared via a two-step interfacial polymerization technique is presented to investigate the effect of the interlayers' pore properties on the performance of the thin-film composite. Nanometer interlayers with different pore sizes are fabricated via interfacial azo-coupling polymerization. The pore properties of the nanointerlayer extremely influence the permeance, where a suitable pore size of 4.22 nm promotes pure water permeance of up to 32.2 L m-2 h-1 bar-1, which is ∼3.8-fold greater than the membrane without an interlayer. However, an interlayer with 0.54 nm pores limits the performance (4.7 L m-2 h-1 bar-1), which is even lower than the unmodified membrane (7.5 L m-2 h-1 bar-1), because of the narrow pores and confined transport mode. However, the confined diffusion rate of amino monomers from the support to interface leads to a thinner PA layer of ∼45 nm and results in high flux. This work provides a facial route for the fabrication of interlayers and facilitate the design of high-performance membrane materials with interlayers.

High-efficiency Pd nanoparticles loaded porous organic polymers membrane catalytic reactors.

An innovative tactic to prepare porous organic polymer membranes was developed via interfacial azo-coupling polymerization. The membranes possess plentiful anchoring sites for loading Pd nanoparticles, and served as a membrane reactor, which exhibits high-performance catalytic reduction with a flux of 27.3 t m-2 day-1 and good long-term stability due to almost zero Pd leaching.

Patterned, anti-fouling membrane with controllable wettability for ultrafast oil/water separation and liquid-liquid extraction.

A novel liquid-infused, patterned, porous membrane system with anti-fouling characteristics is prepared via simple co-infusion of oil and water within hydrophobic and superhydrophilic surfaces of a porous membrane, respectively. This membrane simultaneously repels the immiscible water and oil exhibiting excellent interfacial floatability at the oil-water interface as a separator, thus showing promise for use in applications in the immiscible oil/water separation industry and liquid-liquid extraction.

A liquid-based Janus porous membrane for convenient liquid-liquid extraction and immiscible oil/water separation.

A novel liquid-based Janus porous membrane system was developed through the simple infusion of water and oil within different surfaces. This generates a stable liquid-infusion interface that repels immiscible organic solvents and water, and itself floats at the oil/water interface as a separator. The developed membrane successfully acts as a simple alternative for high-performance liquid separation.

Chlorine-resistant sulfochlorinated and sulfonated polysulfone for reverse osmosis membranes by coating method.

In this work, sulfochlorinated polysulfone (SC-PSf), a functional polysulfone with chlorine resistance, was synthesized through metalation sulfochlorination of polysulfone (PSf). For endowing the required hydrophilicity of SC-PSf, the sulfonyl chloride groups on SC-PSf were partially hydrolyzed to sulfonic groups to produce sulfonated SC-PSf (SC-S-PSf). Thin film composite (TFC) membranes for reverse osmosis application were fabricated by coating solution of SC-S-PSf on porous PSf substrate and then crosslinked by piperazine (PIP) to form polysulfone-sulfamide (PSSA) skin layer. In order to enhance the spreadability of polymer solution on PSf supporting layer, tetrabutylammonium chloride (TBAC), a common surfactant, was added into the coating solution. A flawless membrane was acquired only by a single coating step and at dilute SC-S-PSf solution when TBAC was added into polymer solution. Through optimizing coating conditions, the NaCl rejection and water flux of PSSA membrane reached 96.9% and 17.8 L/m2h under brackish desalination conditions. Moreover, the PSSA membrane exhibited the long-term stability against chlorine during the operation condition of 2000 ppm NaOCl for 10 days. The salt rejection of PSSA only decreased by 1%. In contrast, the salt rejection of polyamide membrane decreased by 8% under the same condition.

Janus porous membrane with conical nanoneedle channel for rapid unidirectional water transport.

The pierced nanowire Janus porous membrane prepared in this study possesses piercing conical nanoneedles, which not only form a transport channel to enhance unidirectional water transport, but also reduce the energy barrier of water transport by changing the route of water transport from droplet to film.

Bioinspired superhydrophilic-hydrophobic integrated surface with conical pattern-shape for self-driven fog collection.

It is well recognized by the scientific community that the fog can be deposited and transported on asymmetric surfaces, thus numerous efforts have been made to create such surfaces. However, it is still challenging to design a surface capable of fast deposition and rapid transportation simultaneously. Herein, inspired by the asymmetric structure of cactus spines and the cooperative hydrophilic/hydrophobic regions of desert beetles, a superhydrophilic-hydrophobic integrated conical stainless steel needle (SHCSN) is fabricated by a facile method. This integrated needle surface combines the merits of the fast deposition of fog on hydrophobic region and then rapid transportation on superhydrophilic surface. The droplet average transportation velocity on SHCSN is greater than other types of surfaces because of large Laplace pressure and self-driven phenomenon at its superhydrophilic-hydrophobic boundary. The best fog harvest efficiency was realized by optimizing the length of the hydrophobic region using theoretical modeling and experimental exploration, whereas the robust superhydrophilic needle surface induced the increase of collection time. This SHCSN was realized to be more efficient in fog collection than uniform superhydrophilic, uniform hydrophobic/superhydrophobic needle surfaces.

Preparation and characterization of an antibacterial ultrafiltration membrane with N-chloramine functional groups.

In this study, a cardo poly(aryl ether ketone) ultrafiltration membrane containing an N-chloramine functional group (PEK-N-Cl membrane) was easily obtained via exposure of a cardo poly(aryl ether ketone) ultrafiltration membrane (PEK-NH membrane) to dilute sodium hypochlorite solution. The chlorination process did not harm membrane performance. In addition, the PEK-N-Cl membrane was stable in both air and water. The PEK-N-Cl membrane exhibited excellent antimicrobial properties against both Gram-negative and Gram-positive bacteria (i.e. E. coli and Bacillus subtilis, respectively). The PEK-N-Cl membrane provided 94.2% and 100% reduction of E. coli and Bacillus subtilis, respectively, within 30min of contact times. Moreover, nearly 100% of the E. coli was killed after 2h during the filtration process for the PEK-N-Cl membrane. In addition, the water flux decreased by 42% for the PEK-N-Cl membrane compared to 77.6% for the PEK-NH membrane after filtration of the E. coli solution and incubation on LB nutrient agar plate, indicating that the PEK-N-Cl membrane enhibits antifouling. Furthermore, the PEK-N-Cl membrane is recyclable via subsequent exposure to a sodium hypochlorite solution.

Mixed-matrix membranes incorporated with porous shape-persistent organic cages for gas separation.

There has been much recent interest in the use of porous materials derived from self-assembling, shape-persistent organic cages due to their solubility and easy post-synthetic modification. Herein we report the preparation of novel mixed-matrix membranes (MMMs) employing the porous organic cage Noria and its derivatives Noria-Boc and Noria-COtBu as the fillers, and a fluorine containing polyimide, 6FDA-DAM, as the polymeric matrix. The physical structures and properties of Noria and its derivatives were measured and investigated. Noria with substituents of Boc (cleaved by thermal treatment during the process of membrane fabrication) and COtBu groups tend to show much better compatibility with polyimide than Noria itself, resulting in homogeneous dispersion of nanoaggregates and fine adhesion between the two phases in the derived Noria/6FDA-DAM and Noria-COtBu/6FDA-DAM MMMs. Gas permeation tests revealed that Noria and Noria-COtBu nanoparticles have different effect on gas separation performance of MMMs. The introduction of Noria into 6FDA-DAM tends to enhance CO2/CH4 selectivity and thus improve its gas separation properties, though a decrease in the observed permeability could be observed. In contrast, the introduction of Noria-COtBu with higher surface area and larger pores tends to increase the free volume and gas permeability of MMMs. These results show that both the morphology and the gas separation properties of MMMs could be tuned by tailoring the structures of porous organic cages.

Thin film composite nanofiltration membranes fabricated from quaternized poly(ether ether ketone) with crosslinkable moiety using a benign solvent.

Thin film composite nanofiltration membranes were fabricated through dip-coating and in situ cross-linking of quaternized poly(ether ether ketone) containing a certain amount of tertiary amine groups (QAPEEKs) on polyacrylonitrile (PAN) support. The effects of the variables in membrane formation such as the coating polymer concentration, the curing temperature, and the cross-linking agent types on resultant membrane were studied and the membrane properties such as the barrier layer chemical structure, the surface element composition and morphology were investigated. The obtained performance of uncross-linked and cross-linked QAPEEK-70 thin film composites in nanofiltration test was compared. The results indicated that the cross-linking improved the composite membranes' performance. For instance, the membrane cross-linked by bisphenol A diglycidyl ether (BPADGE) named M-C-BPADGE exhibited a MgCl2 rejection of 97.8%, a water flux of 11.8Lm(-2)h(-1), a MWCO of 800Da and corresponding pore size of 0.69nm, while for its uncross-linked membrane named M-U, a MgCl2 rejection of 91.2%, a water flux of 13.5Lm(-2)h(-1), a MWCO with 960Da and a pore size of 0.77nm were found. Furthermore, the M-C-BPADGE membrane exhibited selectivities of 16.0 for separation of mixed Mg(2+) and Na(+) cations, much larger than selectivity of 5.2 obtained for M-U, suggesting that the cross-linked membranes are promising in cation separation.

Novel functionalized microporous organic networks based on triphenylphosphine.

This article describes the synthesis and functions of phosphine or phosphine oxide functionalized networks (PP-P or PP-PO; PP = porous polymer). These materials were predominantly microporous and exhibited high surface areas (S(BET): 1284 and 1353 m(2) g(-1) for PP-P and PP-PO, respectively), with high CO2 (2.46 and 3.83 mmol g(-1) for PP-P and PP-PO, respectively) uptake capacities. Pd nanoparticles can be simply incorporated into the functionalized networks (PP-P-Pd or PP-PO-Pd) through a facile one-step impregnation. A yield of 98 % was obtained in the Suzuki reaction between 1-chlorobenzene and p-tolylboronic acid with the PP-P-Pd system, which was higher than that obtained when PP-PO-Pd (53.2 %) or [Pd(PPh3)4] (38.2 %) was used as the catalyst. The superior catalytic ability of PP-P-Pd can be attributed to the structural features that incorporate triarylphosphine within a microporous structure.

Electrochemical route to fabricate film-like conjugated microporous polymers and application for organic electronics.

Film-like conjugated microporous polymers (CMPs) are fabricated by the novel strategy of carbazole-based electropolymerization. The CMP film storing a mass of counterions acting as an anode interlayer provides a significant power-conversion efficiency of 7.56% in polymer solar cells and 20.7 cd A(-1) in polymer light-emitting diodes, demonstrating its universality and potential as an electrode interlayer in organic electronics.

Ultrathin films of organic networks as nanofiltration membranes via solution-based molecular layer deposition.

Ultrathin films of organic networks on various substrates were fabricated through the solution-based molecular layer deposition (MLD) technique. The rigid tetrahedral geometries of polyfunctional amine and acyl chloride involved in the reaction ensure the continuity of the polymerization process. A linear increase in film thickness with respect to cycle number was observed by UV-vis adsorption, ellipsometry, and quartz crystal microbalance. The growth rate per MLD cycle is 1.6 nm, which can be controlled at the single molecular level. For the first time, we develop the MLD method on the top of hydrolyzed PAN substrate, resulting in nanofiltration (NF) membranes. The stepwise growth was monitored via attenuated total reflectance infrared studies. The separation performance of the obtained membrane for various solutes was sensitive to the terminated layers and number of cycles. The rejection of NH(2)-terminated membranes follows the order of CaCl(2) > Na(2)SO(4) > NaCl, while the order for COOH-capped surface is Na(2)SO(4) > CaCl(2) > NaCl. The absolute value of zeta potential for the MLD membranes decreases with the addition of deposition layers. The moderate water flux for the resulting membrane is due to the reduced porosity of the support as well as the low roughness and hydrophilicity of the membrane surface. This bottom-up process provides a promising approach for construction of long-term steady NF membranes with nanoscale dimensions.

Assembly of an unbalanced charged polyampholyte onto Nafion® to produce high-performance composite membranes.

A novel SPES-NH(2)-GA-Nafion® composite membrane with higher proton conductivity and lower methanol permeability was fabricated by covalent crosslinking layer-by-layer self-assembly of an unbalanced charged polyampholyte (SPES-NH(2)) and glutaraldehyde (GA) with controllable free sulfonic acid content.

A novel guanidinium grafted poly(aryl ether sulfone) for high-performance hydroxide exchange membranes.

A novel poly(aryl ether sulfone) ionomer containing hexaalkylguanidinium groups was synthesized, and membranes formed from this polymer displayed large ionic clusters, high hydroxide conductivity, and excellent solubility in low boiling point water-soluble solvents such as ethanol and methanol.

Ionic-liquid-grafted rigid poly(p-phenylene) microspheres: efficient heterogeneous media for metal scavenging and catalysis.

Novel guanidinium ionic liquid-grafted rigid poly(p-phenylene) (PPPIL) microspheres have been developed for metal scavenging and catalysis. The noble-metal nanoparticles supported on the microspheres surface can be used as efficient heterogeneous catalysts. The combination of nanoparticles and ionic liquid fragments on the microsphere surfaces enhance the activity and durability of the catalyst. The PPPILPd(0) catalyst has been tested in the Suzuki cross-coupling reaction, and exhibits much higher catalytic activity than Pd catalysts supported on porous polymer matrices. The PPPILPd(0) catalyst can be recycled at least for nine runs without any significant loss of activity. The present approach may, therefore, have potential applications in transition-metal-nanocatalyzed reactions.