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Heterogeneous catalysis is an important branch of sustainable chemistry. In this work, a series of polyacrylonitrile fiber (PANF) fiber catalysts (PANF-E, PANF-EDs, and PANF-D) with different catalytic micro-environments are developed and characterized by elemental analysis, Fourier-transfer infrared spectroscopy, x-ray diffraction, thermogravimetric/differential scanning calorimetry analysis, scanning electron microscopy, and mechanical strength measurements to demonstrate the successful immobilization of the different amines as well as evaluate the physical strength and thermal stability of the fiber catalysts at different stages. The catalytic activities of the fiber catalysts are tested by one-pot three-component Knoevenagel-Michael reaction to the synthesis of substituted 2-amino-4H-chromenes in which the influences of surface polarities, kinds and proportions of functional groups on the fiber catalysts activities were investigated. Among the prepared catalysts, the PANF-D with higher density of tertiary amino group and hydrophilic micro-environment exhibited the best catalytic activity to efficiently catalyze the three-component reaction in water with excellent substrate suitability (92-98%). In addition, the catalyst can be easily separated from the catalytic system and conveniently reused at least ten times. Moreover, the PANF-D performs well in scaled-up experiment in a simple fixed-bed reactor with a yield of 97% which allows it to have great potential for further cleaner industrial applications. [ABSTRACT FROM AUTHOR]

A series of novel polyacrylonitrile fiber catalysts modified with different ratio of quaternary ammonium salt (QA) to tertiary amine (TA) were screened for heterogeneously catalyzed aza-Michael addition in water. The best catalyst was found to be PANPQ-1F with a QA:TA ratio of 1:1, which can lead to high yield, excellent selectivity of solvent and great recyclability under optimized conditions. The special microenvironment of hydrophilic inner layer and hydrophobic surface layer of PANPQ-1F is conducive to the leaving of the product and the high conversion of the reaction. Based on the fact that appropriate microenvironment combined with the catalytic sites promoted the reaction, cooperative effect of QA and TA in the microenvironment of PANPQ-1F catalyst was proposed. [ABSTRACT FROM AUTHOR]

In this work, we have synthesized a novel hemicyanine-modified polyacrylonitrile fiber (HDBA-PANAF) as a colorimetric Hg2+ sensor. The color is observed from dark red to orange by the naked eye only when the fiber is exposed to Hg2+. Positively, the HDBA-PANAF shows high selectivity and sensitivity for Hg2+ compared with other metal ions such as Na+, Mg2+, Al3+, Ca2+, Cr3+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Cd2+ and Pb2+. Furthermore, the obtained fiber has a wide pH application range from 3 to 11 and also processes a lower detection limit of 1 × 10−6 mol L−1 for Hg2+. Moreover, the HDBA-PANAF undergoes an obvious color change toward Hg2+ even containing an excess of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) in the solution, indicating that the fiber has a stronger complexation affinity for Hg2+ than EDTA-2Na. Hence, the fiber sensor possesses the merits of low cost, high selectivity, low detection limit and environment-friendly property, which shows that it is a promising candidate for Hg2+ detection in water. [ABSTRACT FROM AUTHOR]

ABSTRACT A polyacrylonitrile fiber catalyst with high polar surface micro-environment (C-PANF-Na) was conveniently synthesized and characterized by elemental analysis, Fourier-transfer infrared spectroscopy, UV-vis spectroscopy, scanning electron microscopy, X-ray diffraction, and breaking strength test. The catalytic performance of the fiber was tested by Henry reaction and Gewald reaction in water and favorable results were obtained in terms of high yields, mild conditions, extensive applicability, superior catalytic recyclability, and renewability. It also has advantages of easy preparation, high functional degree, good stability in acid and base, high strength, and good flexibility, and so on. In addition, a high solvent selectivity phenomenon was found in this catalytic system and the reason was explained by proposing a high polar micro-environment effect. Furthermore, the fiber catalyst performed well in scaled-up experiment and flow chemistry experiment, which shows tremendous potential in industrial catalyst as an ideal material for packed bed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45992. [ABSTRACT FROM AUTHOR]

Abstract: The l-lysine functionalized polyacrylonitrile fiber (PANLF) was prepared by grafting the l-lysine into a commercially available polyacrylonitrile fiber and showed highly catalytic activity for Knoevenagel condensation reaction. With low temperature (45 °C) and short reaction time (1 h), the fiber catalyst was well applicable to Knoevenagel condensation of a wide range of aldehydes and the yields could reach up to 99%. Interestingly, only in water could the reaction take place smoothly (with a yield of 88%) and a polar micro-environment promoted reaction process had been proposed to explain this phenomenon. Besides, the fiber catalyst has advantages of easy preparation, high functional degree, strong mechanical strength and thermal stability, etc. And it can be reused at least 5 times without further treatment and performed well in scaled-up experiment (amplified 50 times) and flow chemistry experiment (no loss of catalytic activity after 48 h), which indicates its potential application in industry application.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Polyacrylonitrile fibers were functionalized with different amines to construct special tridimensional catalytic microenvironments at the surface. The polarity of the microenvironments at the surface of the fiber catalyst was tuned by changing the ratio of hydrophobic and hydrophilic amines. The catalytic performances of these microenvironments were examined for a cyanation reaction in water. Among these fiber catalysts with different microenvironments, the one modified with more hydrophobic benzylamine groups (PANBTF) shows much higher catalytic activity than that modified by hydrophilic ethanolamine groups. PANBTF can efficiently and rapidly catalyze the cyanation reaction of benzaldehyde and ethyl cyanoformate in water with a yield of 94 % at room temperature within 40 min. Moreover, a mechanism promoted by the hydrophobic microenvironment has been proposed to explain the high and specific catalytic activity of PANBTF. In addition, this fiber catalyst exhibited excellent recyclability and reusability (8 times) without further treatment, and it also performed well in flow-chemistry tests and scaled-up experiments, which indicated potential for the application of PANBTF in industrial production. [ABSTRACT FROM AUTHOR]

Three chiral pyrrolidine functionalized polyacrylonitrile fiber catalysts have been designed, prepared, and evaluated for their catalytic performance in asymmetric Michael addition of ketones to nitrostyrenes in water. With the optimized catalysts and conditions in hand, their reaction scope for nitrostyrenes was explored. Then the fiber catalysts were further applied to a packed-bed reactor for continuous-flow Michael addition. Based on the fact that organic solvent can inhibit the catalytic activity, a novel microenvironment catalytic mechanism is proposed. [ABSTRACT FROM AUTHOR]

A series of polyacrylonitrile fiber-supported quaternary ammonium salts (PANF-QAS) were prepared and applied to the catalytic reduction of aldehydes, ketones, azides, and benzyl halides in water using NaBH4 as the reducing reagent in a highly efficient, economic, and environmentally benign way. The structure–activity relationships were investigated, which showed that the catalysts made up of quaternary ammonium salts with longer alkyl chains, larger cationic radii and better lipophilicity speed up the reduction reaction to afford the products in excellent yield. Moreover, the optimized catalyst can be applied to the reduction of 1-naphthaldehyde in a continuous flow process with outstanding reactivity and recyclability. [ABSTRACT FROM AUTHOR]

A highly efficient catalytic system composed of a bifunctional polyacrylonitrile fiber (PANF-PA[BnBr]) and a metal chloride was employed to produce 5-hydroxymethylfurfural (HMF) from sucrose in mixed-aqueous systems. The promoter of PANF-PA[BnBr] incorporates protonic acid groups that promote the hydrolysis of the glycosidic bond to convert sucrose into glucose and fructose, and then catalyzes fructose dehydration to HMF, while the ammonium moiety may promote synergetically with the metal chloride the isomerization of glucose to fructose and transfer HMF from the aqueous to the organic phase. The detailed characterization by elemental analysis, FTIR spectroscopy, and SEM confirmed the rangeability of the fiber promoter during the modification and utilization processes. Excellent results in terms of high yield (72.8%) of HMF, superior recyclability (6 cycles) of the process, and effective scale-up and simple separation procedures of the catalytic system were obtained. Moreover, the prominent features (high strength, good flexibility, etc.) of the fibers are very attractive for fix-bed reactor. [ABSTRACT FROM AUTHOR]

A series of new fiber catalysts has been synthesized by aminating a commercially available polyacrylonitrile fiber with polyamines such as diethylenetriamine and triethylenetetramine. These fiber catalysts can efficiently catalyze the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate in water (yields: 95–98%). The triethylenetetramine aminated fiber catalyst was used to catalyze the condensations of a wide range of aromatic aldehydes and active methylene compounds and in each case, this catalyst performed well with yields higher than 93%. This fiber catalyst also exhibited excellent reusability (up to 21 times) and photostability. [ABSTRACT FROM AUTHOR]

A new fiber catalyst for Knoevenagel condensation has been prepared by aminating a commercially available polyacrylonitrile fiber with N,N-dimethyl-1,3-propanediamine. The fiber catalyst was characterized by elemental analysis, X-ray powder diffraction spectra (XRD), scanning electron microscopy (SEM) and Fourier-transfer infrared spectroscopy (FTIR). The Knoevenagel condensation proceeded smoothly in the presence of the fiber catalyst and the products were obtained in excellent yields. This catalyst is applicable to a wide range of aromatic aldehydes. Moreover, the reaction can be easily carried out in different solvents of varying polarities. The newly developed fiber catalyst was also found to exhibit excellent recyclability and reusability (up to 10 times) without any additional treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The preparation method of fiber catalyst is simple. • The reaction was carried out under mild conditions. • The chosen fiber catalyst PAN T-UdA F-I is highly efficient and recyclable. • Possible mechanism based on the fiber's microenvironment is proposed. Fiber-supported quaternary ammonium catalysts for the fixation of CO 2 with epoxides were designed and prepared via amination and quaternization of polyacrylonitrile fiber, followed by ion exchange with different anions. The impact of different quaternary ammonium structures and counter anions on the reaction yields was investigated. A fiber catalyst (PAN T-UdA F-I) with a C 11 carboxylic acid chain and iodide counter anion exhibited excellent catalytic activity in the fixation of CO 2 with epoxides under mild and solvent-free conditions (80 °C, 0.1 MPa) with a very low catalyst amount (0.5 mol%), and diverse cyclic carbonates were obtained in yields between 24–99 %. PAN T-UdA F-I could be conveniently separated by filtration and showed good recyclability and durability till the 4th cycle. Novel cooperative catalytic mechanism is proposed where the ionic microenvironment plays a crucial role to stabilize the ionic intermediates and lowers the activation energy of the reaction. [ABSTRACT FROM AUTHOR]

Abstract: A novel dual colorimetric fiber based on two acid–base indicators was synthesized by first aminating commercially available polyacrylonitrile fiber with tetraethylenepentamine and then covalently immobilizing ethyl orange moieties through an alkylation reaction and a diazo coupling reaction; finally, the fiber was grafted with phenolphthalein using a Mannich reaction. The functionalized fiber was characterized by elemental analysis, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier-transfer infrared spectroscopy (FTIR) and UV–vis spectroscopy, and its color-changing properties, response speed, reusability and photostability were all investigated. This fiber exhibits a remarkable color change from deep pink (pH<1.1) to yellow (1.113.0). Moreover, this fiber shows a fast response time (<1s for 1M HCl and 1M NaOH), high photostability (>60 days) and excellent reusability (>300 times). [Copyright &y& Elsevier]

• Oriented design, facile synthesis and detailed characterization of the novel bifunctionalized fiber catalyst. • Highly selectively catalytic activity for CO 2 cycloaddition with epichlorohydrin under mild conditions. • Simple separation procedure and excellent recyclability of the fiber catalyst-mediated system. Converting CO 2 into useful chemical materials has uniquely high value in both chemical and resource-oriented sense. In this work, several kinds of bifunctional polyacrylonitrile fiber catalysts were developed and applied to selectively catalyze the fixing of CO 2 with epichlorohydrin. Compared to the synergistic effect, the surface polar effect is the major influence factor for the catalytic activity of the fiber catalyst, which is different from other support catalysts and has been explained detailly in this work. Among the synthesized fiber catalysts, benzylamine and N , N' -dimethyl- N -(4-pyridyl)-1,3-propanediamine (DA) bifunctionalized fiber (PAN BD F) has excellent high catalytic activity for its lower polar microenvironment. Different PAN BD Fs with various benzylamine and DA modified degrees were prepared to inspect the influences of benzylamine and DA amounts on the catalytic activity. PAN BD F (benzylamine and DA modified degrees are 0.93 mmol/g and 0.16 mmol/g, respectively) can complete the reaction of epichlorohydrin and CO 2 (97% conversion) under 0.1 mol% catalyst dosage at 80 °C with a CO 2 balloon. Under very low catalyst amount (0.0125 mol%), it can also effectively catalyze the reaction with 56% conversion and the TOF reaches up to 9333.3 h−1. Furthermore, the fiber catalyst can be reused at least five times which indicates a potential to value-added chemistry. [ABSTRACT FROM AUTHOR]

Fiber catalysts with high catalytic activity and good recyclability have attracted much attention. In this work, proton sponge 1,8-bis(dimethylamino)naphthalene functionalized polyacrylonitrile fiber is prepared to construct a superbasic microenvironment, which is applied to catalyze the Knoevenagel condensation in water for the synthesis of α , β -unsaturated compounds. Different characterization techniques of XPS, 13C solid-state NMR, FTIR, SEM etc. Are used to verify the successful grafting of the proton sponge during modification as well as evaluate the stability of the fiber catalyst in specific application. The fiber catalyst exhibits distinctly higher catalytic activity and efficiency in water than in other solvents, with a low catalytic dosage of 5 mol% under room temperature within 3 h. Besides, a synergistic microenvironment can be formed between the hydrophilic polar surface of the fiber and the superbasic catalytic sites, promoting the efficient catalysis of Knoevenagel condensation reaction. In addition, the fiber possesses high reusability that it can be easily recovered and reused for at least 10 times without obvious loss of its catalytic activity. More interestingly, the fiber can be fixed in a reactor to catalyze the Knoevenagel condensation, in which process pure α , β -unsaturated compounds are continuously obtained by simple filtration, avoiding the use of toxic solvents and time-consuming column chromatography, which presents great potential in cleaner and more efficient production. In brief, with such advantages as high catalytic activity, simple separation operation and good economic efficiency, the proton sponge modified fiber is fairly attractive in fixed-bed reactors in cleaner industrial production. A proton sponge functionalized polyacrylonitrile fiber as a superbase heterogeneous catalyst for the preparation of α , β -unsaturated compounds under continuous-flow conditions with high efficiency and excellent reusability. Image 1 ● A novel proton sponge functionalized fiber as superbase catalyst has been synthesized. ● The fiber shows high catalytic performance for the Knoevenagel condensation in water. ● The fiber exhibits high selectivity for solvents and H 2 O is the best reaction medium. ● The fiber catalyst has excellent recyclability for 10 times. ● Effibient synthesis of α , β -unsaturated compounds are achieved under continuous-flow conditions. [ABSTRACT FROM AUTHOR]

• A series of new prolinamide functionalized fiber catalysts are prepared. • The catalytic activity is tuned by linker length and surface microenvironment. • PAN PA−2 F efficiently catalyzes Knoevenagel and related tandem reaction in water. • A possible mechanism for tandem reaction catalyzed is proposed. • PAN PA−2 F performs well in recyclability, flow chemistry and scale-up experiment. A series of new prolinamide polyacrylonitrile fiber catalysts with tunable length of alkyl linker and different linker group were prepared by covalent bonding for the first time and well characterized by mechanical strength, FT-IR, XRD, EA, TGA, SEM and water contact angel. The catalytic activities of these fiber catalysts were evaluated in Knoevenagel condensation and one-pot Knoevenagel-Michael multicomponent tandem reactions to synthesize α , β -unsaturated nitrile and 2-amino-4 H -chromene derivatives in water. The result show that the suitable linker length attaching amines to fiber matrix as well as the constructed hydrophobic microenvironment by linker group within the surface layers of fiber materials effectively promotes the reactions. In addition, the good swollen capacity of fiber in solvent ensure that the reaction proceed well. Fiber catalyst PAN PA−2 F modified by prolinamide with a C2 alkyl chain exhibited the best catalytic performance and can be easily recovered and reused for at least ten consecutive cycles without significant loss of catalytic activity and active sites leaching. [ABSTRACT FROM AUTHOR]

• Prepare a novel quinine functionalized fiber (PAN QN F) used to asymmetric reaction. • The PAN QN F possess high catalytic activity, enantioselectivity and recyclability. • Asymmetric Michael addition is catalyzed excellently by PAN QN F with ee up to greater than 99%. • (S)-2-amino-4H-pyran derivatives are prepared by PAN QN F with ee greater than 99%. As a new type of catalyst support, polyacrylonitrile fiber (PANF) has diverse advantages in physical and chemical properties. Quinine and its derivatives have been widely used as asymmetric organocatalysts recently. By combining the advantages of PANF and quinine, a novel fiber-based asymmetric catalyst (PAN QN F) was successfully prepared through thiol-ene click reaction and characterized by FTIR, XRD, EA, SEM, TGA and mechanical strength analysis. The PAN QN F exhibited excellent catalytic performance for asymmetric Michael addition of malononitrile to chalcone with ee up to > 99%. Further research revealed that the (S)-2-amino-4 H -pyran derivatives were also successfully prepared using PAN QN F as a catalyst in asymmetric tandem Michael addition-nucleophilic annulation of α -phenylchalcone and malononitrile, and the ee of the tandem reaction can also reach greater than 99%. In addition, as an immobilized catalyst, PAN QN F showed relatively wide temperature tolerance and good recycling performance. Overall, the fiber catalyst has the advantages of easy preparation, high activity, high enantioselectivity, wide reaction temperature range, simple separation and good recyclability, which exhibits great potential for industrial application. [ABSTRACT FROM AUTHOR]

A novel mono-quaternary phosphorus salt functionalized fiber (PAN QPS F) was developed as the multifunctional material to simultaneously realize selective removal of sodium dodecyl benzene sulfonate (SDBS) from water and green conversion of CO 2. Compared with other adsorption materials and functionalized fibers, PAN QPS F exhibits the eminent adsorption performance for SDBS due to its high polarization and hydrophobicity, and the adsorption capacity can reach 5.1 mol mol−1, equivalenting to 1066 mg g−1. And the synergistic adsorption mechanism of electrostatic interaction and lipophilic interaction between PAN QPS F and SDBS is proposed. Furthermore, the PAN QPS F still keeps excellent adsorption capacity even after 10 cycles. More satisfactorily, PAN QPS F is used to catalyze the cycloaddition reaction of CO 2 and epoxy compounds. The catalytic mechanism based on the nucleophilicity of Br− and the stabilizing effect of electrostatic interaction is promoted. In summary, the adsorption and catalytic performance prove that PAN QPS F is an outstanding material with multi-dimensional applications. [Display omitted] • A novel mono-quaternary phosphorus salt functionalized polyacrylonitrile fiber (PAN QPS F) was developed. • PAN QPS F can be used to selective removal of sodium dodecyl benzene sulfonate (SDBS) and green conversion of CO 2. • The adsorption capacity for SDBS can reach 1066 mg g−1 and it still keeps excellent adsorption capacity after 10 cycles. [ABSTRACT FROM AUTHOR]

Mercury ions, even an ultra-trace amount in water, present a serious environmental concern. Hence, searching for cost-effective and high-performance Hg 2+ adsorbents has acquired increasingly attention but still remained challenging. In this work, aminophosphonic acid was immobilized onto polyacrylonitrile fiber by chemical grafting approaches. The functionalized fiber (PAN AP F) possessed high adsorption selectivity and efficiency for Hg 2+ when compared with other coexisting ions viz. Pb 2+ , Cd 2+ , Ag + , Zn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Ca 2+ and Mg 2+ . The adsorption results revealed that PAN AP F exhibited high removal capacities for Hg 2+ over a wide pH range from 3 to 11. The adsorption process was better described by the pseudo second-order kinetic model, indicating the chemical interaction between Hg 2+ and active groups on the PAN AP F. Moreover, the maximum adsorption capacity as calculated from the Langmuir adsorption model of 358 mg g −1 was higher than that of many other adsorbents. The PAN AP F could be reused more than 10 times and it is able to decrease Hg 2+ below 50 μg L −1 which is the maximum discharge standard for mercury containing wastewater in China. A continuous-flow process was also implemented to remove Hg 2+ . The results suggested the environmentally friendly PAN AP F could be a promising candidate for Hg 2+ removal in wastewater treatment. [ABSTRACT FROM AUTHOR]

A commercially available synthetic polyacrylonitrile fiber, capable of acting as a novel support for polymer-supported copper catalyst in terminal alkyne homocoupling reactions, is presented. Detailed characterization by inductively coupled plasma (ICP) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) confirmed the changes and stability of the fiber catalyst during the modification and utilization processes. Moreover, the catalytic reactions proceeded at room temperature using air as a green oxidant to afford nearly quantitative yields (95–99%); the fiber catalyst has shown excellent activity and superior recyclability (over 16 cycles); and the procedure is operationally simple and amenable to the gram scale in continuous-flow processing. Furthermore, the prominent features (high strength, good flexibility, etc.) of the polyacrylonitrile fiber make the fiber-supported catalyst very attractive for fixed-bed reactors in the chemical industry. [ABSTRACT FROM AUTHOR]

A carboxymethyl-dithiocarbamate immobilized polyacrylonitrile fiber colorimetric sensor has been synthesized. This fiber sensor exhibits excellent selectivity and sensitivity for Ag + in aqueous solution with a remarkable color change from light pink to red–brown over a wide pH range of 2–12. The sensor responds selectively to Ag + in the presence of other ions, including Mg 2+ , Al 3+ , Ca 2+ , Cr 3+ , Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ and Pb 2+ . The colorimetric sensor has an extremely fast response time (10 s) and a low visual limit of detection (5.53 × 10 −12 mol/L). The fiber sensor also undergoes an obvious color change in the presence of Ag + solutions containing EDTA, NaCl or NaBr. Density functional theory optimization reveals that the sensor and Ag + interact via a seven-membered ring complexation mechanism. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile fiber supported bisquaternary ammonium salts with varying interchain quaternary ammonium (QA) to tertiary amine (TA) ratio, counter ions and linker groups were prepared and characterized by TGA, FTIR, XPS, XRD, SEM, EA and water contact angle. The functionalized fibers were used to catalyze three-component reaction (3CR) and tandem deacetalization-3CR for the synthesis of pyrano[4,3- b ]pyrans, pyrano[3,2- c ]chromenes and pyrano[3,2- c ]quinolines in ethanol-water mixture. Under varying reaction conditions such as time, temperature, catalyst amount and solvents, the catalytic ability of the prepared fiber catalyst was investigated. Under the optimum conditions, the bisquaternary ammonium fiber with acetate counter ion and an interchain QA to TA ratio of 1:1 (PAN BQAc F) showed the best catalytic activity among the prepared fiber catalysts, and it can be used for 10 runs consecutively with only a slight depreciation in catalytic activity. Interestingly, PAN BQAc F can efficiently catalyze tandem deacetalization-Knoevenagel reaction and the relevant novel tandem deacetalization-3CRs for the synthesis of pyran-annulated heterocycles. In the tandem deacetalization reactions, the acetate ion plays an important role of facilitating proton transfer, which makes PAN BQAc F a cooperative and reusable heterogeneous catalyst. [Display omitted] • Novel tandem deacetalization-three component reactions were catalyzed successfully. • Performance depends on ratio of bisquaternary ammonium to tertiary amine moieties. • BQA moiety aids in-situ acid-base property, hydrophilicity and polarity of the fiber. • Excellent catalyst reusability was achieved up to 10 runs with high yields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel Pd(0) nanoparticle-functionalized polyacrylonitrile fibers have been prepared. • The chosen fiber catalyst PAN GQA F-Pd(0) is highly efficient and recyclable. • Possible mechanism based on the fiber's microenvironment is proposed. Palladium salts and Pd(0) nanoparticles were immobilized on a series of amine and quaternary ammonium functionalized polyacrylonitrile fibers (PANFs) to prepare functionalized fiber catalysts. The catalytic activities of these materials for Heck reaction were investigated. Among which, the Gemini quaternary ammonium fiber immobilized Pd(0) nanoparticles catalyst PAN GQA F-Pd(0) exhibited the best catalytic activity, which was able to effectively catalyze Heck reaction and 4-nitrophenol (4-NP) reduction with high yields of 76–99%. And the catalyst can tolerate an extensive scope of substrates under mild reaction conditions. In addition, PAN GQA F-Pd(0) was easily recovered, and it can be reused 10 times with little decrease in catalytic activity and low Pd leaching (only 3.69%). The experimental results confirmed that Pd(II) was converted into Pd(0) during the coupling reactions, which helped to promote the reaction. This explains why the catalytic activity of PANF-immobilized Pd(0) is better than that of PANF-immobilized Pd(II). Accordingly, possible mechanisms for the catalytic Heck reaction and reduction reaction of PAN GQA F-Pd(0) were proposed. [ABSTRACT FROM AUTHOR]

Abstract: A tertiary amine immobilized fiber was prepared and used to efficiently catalyze tandem Michael–intramolecular Henry reactions between 1,4-dithiane-2,5-diol and trans-β-nitrostyrenes to form the corresponding tetrahydrothiophene derivatives. This newly developed fiber catalyst is applicable to a wide range of trans-β-nitroalkenes and affords good to excellent yields (75–93%) under mild conditions (with 2.5 mol % fiber catalyst at 50 °C in ethanol for 5 h). The fiber catalyst exhibits excellent recyclability and reusability (up to 10 times) after simple workup procedure with only a slight loss in catalytic activity. It is noteworthy that the major diastereomers have r-R, trans-nitro, trans-hydroxy configurations with diastereoselectivities of up to 15:1. This differs from the results obtained when the same reaction is catalyzed by a homogeneous catalyst. This is the first example of a fiber catalyst exhibiting excellent diastereoselectivity. [Copyright &y& Elsevier]

A novel carbohydrazide functionalized polyacrylonitrile fiber (PAN J F) was designed and prepared for removal of furfural from water. Compared with other amino-containing functionalized fibers, the PAN J F fiber exhibits the highest adsorption capacity due to the highest reactivity of carbohydrazide. Batch experiments were performed to explore the influence of pH, initial concentration of furfural, dosage of adsorbent, adsorption time, and temperature on the process of adsorption. Under the optimized condition, the maximum adsorption capacity of PAN J F for furfural reaches 140.4 mg g−1. Kinetic and isothermal curves show that the adsorption process is in accordance with the pseudo-second-order model and the Langmuir isothermal adsorption model. Furthermore, the thermodynamic result indicates that the furfural adsorption on PAN J F is an endothermic and spontaneous process. More satisfactorily, the PAN J F still maintains 90% removal efficiency even after five cycles, which certifies it is an excellent scavenger and can be utilized to remove furfural in practice. [Display omitted] • A novel carbohydrazide functionalized polyacrylonitrile fiber (PAN J F) was designed. • PAN J F can remove the furfural from wastewater. • The maximum adsorption capacity of PAN J F for furfural can reach 140.4 mg g−1. • PAN J F still maintains 90% removal efficiency even after five cycles. [ABSTRACT FROM AUTHOR]

A series of polyacrylonitrile fibers (PANF) functionalized with nitrogen-containing ligands were prepared and then used to synthesize fiber-supported Pd(0) nanoparticle catalysts. The phenanthroline-functionalized PANF with immobilized Pd(0) nanoparticles (PAN Phen F-Pd(0)) had the best catalytic activity for the Heck reaction under solvent-free conditions. The PAN Phen F-Pd(0) efficiently stabilized the nanoparticles and they were well-dispersed with Pd(0) particle sizes of about 3 nm. The PAN Phen F-Pd(0) structure was further characterized by a variety of instrumental methods. A probable mechanism based on the fiber's microenvironment is proposed for the Heck reaction catalyzed by PAN Phen F-Pd(0). The PAN Phen F-Pd(0) catalyst is easily recovered from the reaction system and can be used up to six times with only a slight decrease in catalytic activity and with low Pd leaching. The PAN Phen F-Pd(0) catalyst also has excellent catalytic activity for gram-scale use. [Display omitted] • Novel Pd(0) nanoparticle-functionalized polyacrylonitrile fibers serve as catalysts to catalyze Heck reaction. • The chosen fiber catalyst PAN Phen F-Pd(0) is highly efficient, selective and recyclable. • Possible mechanism based on the fiber's microenvironment is proposed. [ABSTRACT FROM AUTHOR]

A series of polyacrylonitrile fiber (PANF)-supported copper(II) catalysts were prepared through the immobilization of Cu(II) into prolinamide-modified PANF (PAN PA-2 F) and subsequently used for the synthesis of diverse N -arylimidazoles from arylboronic acids and imidazole. The prepared Cu(II)@PAN PA-2 Fs were well characterized by mechanical strength, FT-IR, XRD, XPS and SEM. Among them, CuCl 2 @PAN PA-2 F exhibited excellent catalytic performance, and its activity was significantly affected by the Cu loading. This catalytic system also displayed good activity in the synthesis of N -arylsulfonamides from arylboronic acids and tosyl azide. It was highly efficient in gram-scale reactions and could be reused five times. The advantages of low cost, easy preparation, good durability and facile recovery make the fiber catalyst attractive. Unlabelled Image • Prolinamide-functionalized polyacrylonitrile fiber (PAN PA-2 F) was used to immobilize copper (II) as a novel support. • Cu content was easily adjusted based on various functional degree of PAN PA-2 F. • The cupric chloride-immobilized fiber showed excellent activity in base-free Chan-Lam coupling reactions. • The fiber catalyst can be easily recycled and reused for 5 runs. [ABSTRACT FROM AUTHOR]

• Amine-functionalized fibers with surface wettability modification are prepared. • Enhanced catalytic activity is achieved by introducing hydroxyl group to fiber. • Hydrophilic prolinamide fiber shows high activity and selectivity in aldol reaction. • Fiber catalyst can be easily recovered and reused for at least seven times. Heterogeneous catalytic aldol reaction has widely focused on tethering multiple functional groups upon support that can act together (for example, acid-base cooperation) to improve reaction rate beyond individual moiety alone. Here, a series of amine-functionalized fibers with additional surface wettability modification were prepared to promote aldol reaction in water. The result showed that an enhanced catalytic activity was achieved by introducing hydroxyl group to fiber. Hydrophilic prolinamide-functionalized fiber (PAN E F-PLA) exhibited the best catalytic performance, and its activity proved to be higher than those of hydrophobic-modified fiber and even the small molecule prolinamide. This enhancement is attributed to that the favorable hydrophilic microenvironment consisting of hydroxyl group, residual cyano group and prolinamide facilitates the accessibility of reactants to catalytic sites and increases the rate of mass transfer in water for promoting reaction. This work provides an effective protocol to maximize performance of fiber-supported catalyst by appropriate wettability modification. [ABSTRACT FROM AUTHOR]

Thirteen novel amine or quaternary ammonium functionalized polyacrylonitrile fiber (PANF) supported phosphotungstic acid (PTA) catalysts were designed and prepared, and their catalytic activities were screened by choosing condensation/annulation tandem synthesis of 2,3-dihydroquinazolin-4(1 H)-one compound via C–N bond formation between 2-aminobenzamide and p -chlorobenzaldehyde as a model reaction. By adjusting the functionality and hydrophobic/hydrophilic property of the amine/ammonium structure as well as the density of PTA sites, the fiber catalyst CAT-12 prepared from quaternary ammonium functionalized PANF containing benzyl group with high PTA loading achieved the best catalytic activity for most reactions in water. The CAT-12 can be easily separated from the reaction system and recycled for 7 times without significant loss of catalytic activity. Moreover, the reaction proceeded smoothly in gram scale and gave nearly quantitative yield using this efficient, eco-friendly and easily recyclable catalyst with great industrial potential which was also demonstrated in Friedel-Crafts alkylation of indoles with β -nitrostyrene. Vivid PTA immobilization processes and the corresponding "catch-catalyze" catalytic modes were further schematically described to address the effect of microenvironment-tuning on immobilization and catalysis, and accordingly the possible catalytic mechanisms of the two reactions were proposed. Image 1 • Novel acid-functionalized PANFs serve as tunable catalysts to synthesize derivatives of heterocyclic compounds. • The chosen fiber catalyst CAT-12 is highly efficient, selective and recyclable. • Possible "catch-catalyze" pattern based on the fiber's microenvironment is newly proposed. [ABSTRACT FROM AUTHOR]

Adsorption is one of the most effective methods to remove organic pollutants from water. A series of functionalized fiber adsorbents with cationic adsorption sites and different hydrophobic alkyl chains have been prepared by immobilizing quaternary ammonium salts (QASs) on polyacrylonitrile fiber (PANF). The hydrophobicities of these QAS-functionalized fibers were evaluated by water uptake and contact angle analysis. These fibers were employed to remove anionic azo dyes (methyl orange, alizarin yellow R and methyl red from water. The fiber with a twelve-carbon alkyl chain (designated PAN QAS-12 F) had the highest adsorption capacity for MO and the maximum adsorption capacity (Q e) is 1.82 mmol g-1. The PAN QAS-12 F dye adsorption process follows second-order kinetics and correlates with a Langmuir model. A possible adsorption mechanism that proposes electrostatic interactions as the primary interactive force and hydrophobic and weak hydrogen bonding interactions as secondary forces is presented. The QAS-functionalized fiber can be reused ten times while still maintaining a removal rate of 99% or higher. The QAS-functionalized fiber is also very suitable for continuous flow processes giving a MO removal rate of more than 90% for the treatment up to 1020 mL of MO-containing water. These QAS-functionalized fibers have very promising application potential. • Simple preparation method. • Large amount of adsorption. • Environment friendly. • The removal rate of 10 cycles is more than 90%. • Suitable for continuous flow process. [ABSTRACT FROM AUTHOR]

A series of anionic functionalized polyacrylonitrile fibers were prepared and used to remove cationic dyes from water. The phenolate immobilized fiber (PAN P(−) F) exhibited excellent adsorption capacities for cationic dyes, among which the best results was obtained for Brilliant cresyl blue (BCB) with color changing of the solution from sapphire to light yellow. Additionally, PAN P(−) F can selectively remove cationic dyes from dye mixtures containing both anionic and cationic dyes. After acid-base regulating, the highest adsorption capacity of PAN P(−) F was obtained at pH 10. Moreover, adsorption kinetic illustrated that PAN P(−) F can achieve half adsorption capacity within 10 mins and follow pseudo-second-order model. The maximum adsorption capacity calculated from isotherms experiments reached 2.306 mmol/g (890.1 mg/g) at 25 °C. The activation energy of the adsorption process was 30.74 kJ/mol indicating that the BCB adsorption process occurs via chemical adsorption. Furthermore, the PAN P(−) F can be readily separated from solution and reused 10 cycles. Under a continuous flow condition, the BCB concentration can be reduced to 20 ppb at first and remained below 1.69 ppm during the 825 mins adsorption process. At the same time, the removal ratio kept above 98.31%. In general, this novel PAN P(−) F adsorbent is eco-friendly, highly efficient, selective, reusable, and has great potential for the removal of dyes from industrial wastewaters. • Novel anionic functionalized polyacrylonitrile fibers serve as reusable adsorbents to remove cationic dyes from water. • The PAN P(−) F shows high selectivity and efficiency for BCB (brilliant cresyl blue) removal. • The PAN P(−) F can decrease BCB concentration as low as 20 ppb. • The PAN P(−) F has excellent reusability for more than 10 times. • The PAN P(−) F can be used in a continuous flow process with high removal efficiency. [ABSTRACT FROM AUTHOR]

Title reaction synthesizes bis(indolyl)methanes under mild and environmentally friendly conditions in high yields. [ABSTRACT FROM AUTHOR]

The synthesis of the catalyst and its recyclability (ten cycles without loss of activity) is described. [ABSTRACT FROM AUTHOR]

The newly developed title catalyst is successfully employed for the diastereoselective synthesis of tetrahydrothiophenes via tandem Michael/intramolecular Henry reactions between nitrostyrenes and 1,4-dithiane-2,5-diol. [ABSTRACT FROM AUTHOR]