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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]

The preparation and application of fiber catalysts have attracted much attention. However, research on the effect of the micro-environment of fiber catalysts on the catalytic activities though of special importance is limited. In this work, a novel strategy for the synthesis of phosphoric acid-functionalized polyacrylonitrile fibers with a polarity tunable surface micro-environment by hydrophobic groups for one-pot C–C and C–N bond formation reactions is reported. The special hydrophobic surface micro-environment of the fiber catalysts is proven to promote the catalytic activities impressively in cyclocondensation of β-ketoesters with 2-aminobenzamides, the Knoevenagel condensation as well as the multi-component Biginelli reactions in green solvents. Both the surface synergy of the catalytic sites and hydrophobic auxiliary groups (benzyl or n-butyl) in the surface of fiber catalysts and interface acceleration in reaction medium play an important role in the highly efficient promotion of catalytic activity. Thereby a surface synergistic mechanism is proposed to explain the micro-environment effect. In addition, the fiber catalysts could be simply separated from the reaction system using tweezers and directly used in the next cycle without further treatment. Importantly, even after 10 reaction cycles in water or ethanol, there is no significant loss in their catalytic activity. The results indicate that the phosphoric acid functionalized fibers show green and sustainable potential for industrial production. [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]

The electrospinning method combined with high temperature thermal annealing was used to prepare TiO 2 fibers modified with different concentrations of Co 3 O 4. Field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), desktop scanning electron microscope (TM3030)-energy spectrometer (SwiftED3000), thermal analyzer (TGA), X-ray diffractometer (XRD), X-ray photoelectron energy Spectral analyzer (XPS), Brunauer–Emmett–Teller (BET) (BET) were used to study the influence of different cobalt oxide concentrations on the morphology of mesoporous TiO 2 fibers. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and continuous cycle method were used to evaluate the fiber's oxygen evolution reaction (OER) and oxygen reduction (ORR) reactivity. It was found that the fiber with a molar ratio of Co to Ti of 1:10 showed the best performance for both OER and ORR reactions in alkaline solution. The fiber showed an overpotential of 382 mV at a current density of 10 mA cm−2, a Tafel slope of 58 mV·dec−1, and a half-wave potential change of only 10 mV after 4000 CV cycles. It has an onset potential of 0.83 V (vs RHE) in the ORR reaction. The OER/ORR overpotential gap (E) of 0.85 V is significantly lower than commercial platinum/carbon and bulk TiO 2 analogs. Obviously, this catalytic activity stems from the synergy between Co 3 O 4 and TiO 2 fibers. In addition, the higher specific surface area and the presence of disordered mesopores provide a higher charge carrier density during the electrocatalytic process, which improves the reaction activity. [Display omitted] • TiO 2 was adopted in present research to replace carbon as a catalyst support substrate. • The Co 3 O 4 @TiO 2 nanofiber possess an unique mesoporous structure, which provides more active sites for the reaction, and makes good catalytic performance for the reaction through the synergistic of TiO 2 and Co 3 O 4. • The Co 3 O 4 @TiO 2 nanofibers show good catalytic performance for both the OERand ORR. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fibrous superbase catalyst for organic conversions in continuous-flow processing. • Powerful combination of support and catalyst for prominent application performance. • Highly catalytic activity and general applicability for the mediated reactions. • Superior stability and strong practicality for efficient scale-up procedure. The development of clean catalytic technologies in continuous-flow processing for efficient organic conversions has a positive influence on the fine chemicals and pharmaceutical manufacturing. Herein, the commonly used organic superbase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was immobilized on the commercially available ultra-high strength textile fiber polyetheretherketone (PEEK) to report a polymer-supported basic catalyst (PEEK-TBD) for three types of organic conversions in cleaner continuous-flow processing. The fiber catalyst was prepared through an improvement strategy and verified as a heterogeneous fibrous superbase catalyst in the microtubule reactor to mediate the Knoevenagel condensation-cyclization between salicylaldehydes and activated nitriles for the synthesis of iminocoumarins in ethanol (10 samples, yields 91–97%) after turning the flow rate, substrate concentration, and catalyst padding quantity, additionally, PEEK-TBD was also effective for the cyanosilylation of carbonyl compounds for the synthesis of cyanogen compounds in acetonitrile, as well as the substitution reaction of aniline and carbonate for the synthesis of N , N '-substituted urea in toluene in continuous-flow processing. Moreover, the resulting fiber samples were characterized in detail by sorts of analytical methods and techniques to further confirm the dependability of this methodology, and the clean and valid gram-scalable procedure of PEEK-TBD in continuous-flow processing has extensive application prospects on the chemical productions. [ABSTRACT FROM AUTHOR]

• Facile synthesis and detailed characterization. • High catalytic activity and substrate selectivity. • Prominent recyclability and superior stability. • Extremely simple separation procedure and efficient scaled-up process on a simple fixed-bed reactor. Acid-base bifunctional catalysis represents a significant approach for achieving enzyme-like catalytic activity. In this study, we present a concise and direct approach for constructing acid-base bifunctional aramid fiber catalysts, enabling one-pot tandem deacetalization-Knoevenagel reactions in an aqueous environment. The fiber catalysts were conveniently prepared from commercially available aramid fiber using a straightforward two-step procedure, and comprehensively characterized using various detection techniques. Additionally, the acid-base cooperativity of the AF catalyst was effectively controlled through the manipulation of the acid-base ratios within the catalysts. Notably, the AF-SN1/2 catalyst exhibited superior catalytic activity in the one-pot tandem deprotection-Knoevenagel reaction at room temperature, resulting in the production of high yields. Moreover, the AF-SN1/2 catalyst demonstrated exceptional recyclability and performed admirably in a scaled-up experiment utilizing a straightforward fixed-bed reactor. These findings suggest that the AF-SN1/2 catalyst holds significant promise for future applications in cleaner industrial processes. [Display omitted] [ABSTRACT FROM AUTHOR]

• 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]

• 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]

[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]

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]

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