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We describe tandem response nanochannels tailored with a porphyrin derivative that showed Zn2+ and NO gating with good stability and reversibility.

We describe functional two-dimensional materials via the combination of pillar[5]arene and MXene, which exhibit high supramolecular recognition, enrichment capability, and high electrochemical response toward dye molecules.

A tunable strategy to prepare α,β-unsaturated esters and α,β-unsaturated-γ-keto esters in good to excellent yields was developed through copper-catalyzed oxidative coupling of phosphorus ylides with alkenyl boronic acids under mild conditions. The reaction without water afforded α,β-unsaturated esters, ketones, and amides while α,β-unsaturated-γ-keto esters, 1,4-α,β-unsaturated diketones and α,β-unsaturated-γ-keto amides were obtained when using 5.0 equiv. of water. H2O18 labeling experiments showed that water played an important role in the formation of α,β-unsaturated-γ-keto esters. A plausible formation mechanism for α,β-unsaturated esters and α,β-unsaturated-γ-keto esters was proposed based on mechanistic studies. Phosphonium salts could also be used directly as coupling partners instead of phosphorus ylides. The reaction exhibited a broad substrate scope, good functional group tolerance, good regioselectivity, and diverse coupling products.

A variety of functionalized 2-substituted benzoxazoles can be prepared in good yields from amidoximes and diaryliodonium salts by selective O-arylation and sequential [3,3]-rearrangement under metal-free conditions. O-arylation of amidoximes was promoted by 3 A molecule sieves in the absence of a base and a sequential TFA-mediated [3,3]-rearrangement was used to synthesize 2-substituted benzoxazoles. Both of the O-aryl products and rearrangement products were compatible with a broad range of sensitive functional groups such as ester, aldehyde, nitro, vinyl, amine, and amide groups in addition to halides. A bidentate N-ligand with double benzoxazoles was prepared at gram-scale in two steps.

A metal-free construction of highly diastereoselective nine-membered heterocycles is described via the cycloaddition and rearrangement of N-vinyl-α,β-unsaturated ketonitrones and isocyanates. Notably, the prepared nine-membered heterocycles afforded 2,3-dihydropyrrolizines under heating conditions. Mechanistic studies showed that the nine-membered rings might undergo decarboxylation, isomerization, aza-Michael addition, and aromatization to afford 2,3-dihydropyrrolizines in a one-pot reaction.

An efficient synthesis of 1-vinyl/aryl benzotriazole 3-oxides via the copper-promoted coupling of N-hydroxybenzotriazoles with alkenyl or aryl boronic acids is reported. This strategy features mild reaction conditions, good functional group tolerance, broad substrate scope and rapid introduction of benzotriazole N-oxides moieties into molecules. Density functional theory calculations revealed that the formation of the favored N-coupling product depends on the kinetically more favorable C−N bond formation pathway.

Sodium alginate (SA), known as a type of polysaccharide, was one of the main foulants in a water ultrafiltration (UF) system. In this study, internal membrane fouling of rhodamine-labeled SA filtration through polyethersulfone (PES) UF hollow-fiber membranes was directly observed using fluorescent microscopy. Different molecular weight cut-offs (MWCOs) and morphologies of PES membranes resulted in different internal accumulation of SA in membranes. Fluorescent microscope images showed that SA molecules tended to accumulate at the vacant spaces inside membranes without forming a foulant layer on membrane surfaces during filtration. SA that accumulated at the vacant spaces was removed by backwashing. Filtration types (inner-pressured and outer-pressured) also affected internal fouling of SA due to asymmetric structures of PES membranes, regardless of the similar flux and rejection results between the filtration types. Understanding internal fouling provides important insights into membrane fouling and usefu...

Catalytic conversion of i -butane over Zn-modified HZSM-5 catalyst was systematically investigated at different reaction pressures. A special fixed-bed reactor involving a vacuum unit which could modulate reaction pressure from subatmospheric to positive pressure was used. Results show that reaction pressure can change the initial activation and subsequent reaction paths of i -butane over Zn/HZSM-5 catalyst. At subatmospheric pressure, the decrease in reaction pressure favors the dehydrogenation of i -butane, meanwhile inhibits both the cracking of i -butane and the secondary reactions such as the oligomerization, cracking and aromatization. Consequently, the selectivities to the undesired by-products (methane and ethane) are notably abated, and the selectivities to the desired products (ethylene, propylene and aromatics) significantly increase. Although space velocity affects the reaction paths for i -butane conversion, the change in reaction pressure has a more profound effect on the reaction paths.

Membrane fouling caused by macromolecular species such as proteins remains a major problem, especially in ultrafiltration processes. In this work, we developed a method of direct observation of protein fouling inside a hollow-fiber membrane using fluorescent microscopy. Fluorescent microscope images showed where proteins accumulated inside the membrane during filtration. Commercially available membranes with differing molecular weight cutoffs had differing geometries of internal protein deposition. Different types of proteins (BSA, casein, and lysozyme) also induced different internal membrane foulings. Poly(vinylidene fluoride) hollow-fiber membranes with and without a skin layer were prepared by phase separation methods, and the present observation method revealed that the structural differences between the membranes significantly affected internal membrane fouling. Finally, the protein-fouled membrane was backwashed with various cleaning agents. The fluorescent microscopic observation visualized the ef...

Precipitation polymerizations of divinylbenzene (DVB) in pure supercritical carbon dioxide, and parallel runs with presence of a cosolvent were carried out. The results showed that use of acetone as the cosolvent contributed greatly to the formation of the monodisperse microspheres. PDVB microspheres, with obviously higher uniformity than reported up to date, were achieved using 6–7 mL of acetone in a reactor of 50 mL with DVB concentration of 0.4 mol/L under 16 MPa, a much lower pressure than previously reported without use of cosolvent.

The influence of chemical compositions on the properties of sulfonated poly(arylene ether sulfone)-based proton-exchange membranes was studied. First, we synthesized three different series of random SPAES copolymers using three kinds of hydrophobic monomers, including 4,4′-dihydroxyldiphenylether, 2,6-dihydroxynaphthalene (DHN), and 4,4′-hexafluoroisopropylidenediphenol (6F-BPA) to investigate effects of hydrophobic components on the properties of SPAES membranes as proton-exchange membranes. Random SPAES copolymers with 6F-BPA showed the highest proton conductivity while random SPAES copolymers with DHN displayed the lowest methanol permeability among the three random copolymers. Subsequently, we synthesized multiblock SPAES using the DHN as a hydrophobic monomer and studied the effect of the length of hydrophilic segments in the multiblock SPAES copolymers on membrane performance. The results indicated that longer hydrophilic segments in the copolymers led to higher water uptake, proton conductivity, and proton/methanol selectivity of membranes even at low humidity. In addition, the morphology studies (AFM and SAXS measurements) of membranes suggested that multiblock copolymers with long hydrophilic segments resulted in developed phase separation in membranes, and ionic clusters formed more easily, thus improving the membrane performance. Therefore, both the kinds of hydrophobic monomers and the length of hydrophilic segments in SPAES copolymers would influence the membranes performance as proton-exchange membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Random and multiblock copolymers of sulfonated poly(arylene ether sulfone) (SPAES) were synthesized and characterized to compare the differences in the properties of proton-exchange membranes made with random and multiblock SPAES copolymers. Atomic force microscopy observations and small-angle X-ray scattering measurements suggested the presence of nanoscale, clusterlike structures in the multiblock SPAES copolymers but not in the random SPAES copolymers. Proton-exchange membranes were prepared from random and multiblock copolymers with various ion-exchange capacities (IECs). The water uptake, proton conductivity, and methanol permeability of the SPAES membranes depended on the IECs of the random and multiblock SPAES copolymers. At the same IEC, the multiblock SPAES copolymers exhibited higher performances with respect to proton conductivity and proton/methanol permeation selectivity than the random SPAES copolymers. The higher performances of the multiblock SPAES copolymers were thought to be due to their clusterlike structure, which was similar to the ionic cluster of a Nafion membrane. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Sulfonated poly(arylene ether sulfone) (SPAES)/polystyrene(PS) and SPAES/polystyrene sulfonic acid (PSSA) composite membranes were studied for a proton-exchange membrane used in a fuel cell. PS microspheres were synthesized by emulsion polymerization. PSSA microspheres with 5.3 mmol/g ion-exchange capacity (IEC) were prepared by sulfonation of PS microspheres. The composite membranes were prepared by solution casting. SPAES/PSSA composite membranes showed higher proton conductivity than a SPAES membrane because of the IEC improved by adding PSSA. Although the addition of PSSA also brought about the increase of a methanol permeability, the proton/methanol selectivity defined as the ratio of the proton conductivity to the methanol permeability was improved at low humidity by adding 5 wt % of PSSA microspheres. Differential scanning calorimetry results indicated that the amount of free water varied in the cases of the addition of the two kinds of organic microspheres. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008