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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]

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]

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 In this paper, basalt fibers (BF) was employed as high modulus component with good interface bonding with cement matrix to enhance local stress applied on piezoelectric ceramic particles in 0–3 cementitious piezoelectric composites (0–3 CPCs). The effect of content of BF varying from 0.00 vol% to 0.23 vol% on the mechanical, piezoelectric and dielectric properties of 0–3 CPCs and the output voltage of 0–3 CPCs sensor was evaluated. The results showed that amplitude of output voltage of the 0–3 CPCs sensor with 0.12 vol% BF maximized at 4.98 V, which was 60.0% higher than that of the 0–3 CPCs sensor without fibers for the compact structure of the 0–3 CPCs and good interface bonding between BF and cement matrix as a reason of good stress transfer in the composites. While the split tensile strength, piezoelectric voltage constant (g 33), piezoelectric strain constant (d 33), relative dielectric constant (ε r) and dissipation factor (tanδ) was 13.1 MPa, 11.36 × 10−3 V m/N, 43 pC/N, 430.0 and 0.43, respectively. It provided a novel method to improve the mechanical-electrical response of piezoelectric sensor by enhancing local stress applied on piezoelectric ceramic particles in the piezoelectric composites. [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]

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]

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]

[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 new wearable colorimetric fiber for heavy metal ion detection and adsorption has been synthesized by first aminating a commercially available polyacrylonitrile fiber with ethylenediamine and then covalently immobilizing 4-(2-pyridylazo)-1,3-benzenediol (PAR) on the modified fiber through a Mannich reaction. The fiber was characterized by X-ray powder diffraction spectra (XRD), scanning electron microscope (SEM), FTIR and UV–vis spectroscopy, and its acid exchange capacity, colorimetric properties, response speed, selectivity, reusability, photostability and adsorption capacity were investigated. In neutral aqueous solutions, the PAR immobilized fiber responds selectively to heavy metal ions, such as Hg2+, Pb2+, Cd2+, Zn2+, Ni2+ and Cu2+ with a color change from red-orange to dark-brown. Its visual detection limit for Pb2+ is 1×10−6 mol/L. Moreover, the selectivity increases with a decrease in pH, i.e. at pH 3.0, it shows a color change only for Hg2+ and Cu2+. This fiber also shows excellent reusability (>50 times), high photostability (>30 days under direct exposure to sunlight) and high adsorption capacity for Hg2+ (0.74mmol/g). [Copyright &y& Elsevier]

Abstract: A novel halochromic fiber was synthesized by first aminating commercially available polyacrylonitrile fiber with ethylenediamine and then immobilizing phenolphthalein covalently through a Mannich reaction. The fiber was characterized by XRD, SEM, FTIR and UV–vis spectroscopy. The halochromic properties, response speed and durability of this functional fiber have been investigated. This halochromic fiber exhibited remarkable color change from pale yellow to violet in a wide range of alkaline solutions (pH>10.1) with short response time (<1s for 20wt-% NaOH) and strong recycle stability (>300 times). [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]

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]