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Heterogeneous catalysis is an important way to realize green chemistry. Developing excellent heterogeneous catalysts by using appropriate supports is still a mainstream research area. Polyacrylonitrile fiber (PANF), a common textile material in our daily life, has excellent advantages of low cost, high strength, light density, mildew resistance, etc. Furthermore, PANF can be knitted into varieties of shapes, making them very suitable for fixed‐bed catalysis in industries. Consequently, PANF is a fine raw material for the synthesis of heterogeneous catalysts. Therefore, more and more PANF‐based heterogeneous catalysts had been developed and applied to various of reaction systems. In this paper, the research progress of PANF‐based catalysts was reviewed, and the research progress of different PANF catalytic systems and their applications in green chemistry were emphatically introduced, which provided reference to the development of PANF‐supported catalytic technology. Finally, the catalytic system supported by PANF is summarized and prospected. [ABSTRACT FROM AUTHOR]

A novel solid acid catalyst (PANEAPF) is developed by immobilization of phosphoric acid on polyacrylonitrile fiber through covalent bonding. Various characterization techniques such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), etc. are utilized to confirm the successful grafting and the stability of the fiber catalysts during application. PANEAPF shows high catalytic activity in the acetalization of aldehydes owing to the high utilization efficiency of its functionalized acid sites. In addition, the strong polarity micro-environment in the surface layers of PANEAPF make it highly suitable for catalytic application in both water and alcohol. Furthermore, the fiber catalyst can be applied to the acetalization of aldehydes in a continuous-flow process at room temperature, and shows excellent reactivity and superior recyclability (over 20 times). The many advantages of PANEAPF such as simple preparation, convenient regulation of acid amount, high durability, and eco-friendly process make it very attractive for fixed-bed reactors in the chemical industry. [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]

• 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]

Abstract Two fiber supported tertiary amine catalysts were prepared by immobilization of 3-dimethylamino-1-propylamine (PAN D F) and 3-dimethylamino- N -methylpropylamine (PAN T F) on polyacrylonitrile fiber. Both fiber catalysts contain polar microenvironments constructed by amide groups, tertiary amine groups and unreacted cyano groups. The difference between the two catalysts lies in that the PAN D F contains hydrogen bond network while the PAN T F does not. Employing Knoevenagel condensation as a model reaction, the cooperative action of immobilized tertiary amines with hydrogen bonds was evaluated in detail. At the same time, the aggregation of reactants in the polar microenvironment under different solvents was also investigated. The results showed that hydrogen bonds and the supporting basic groups can promote the reaction by the synergistic catalytic effect in most solvents. The catalysts displayed different catalytic behaviors in solvents with different polarities. The catalysts can achieve highly efficient catalytic activity in the more polar solvents which were well compatible with the catalysts. Moreover, the reaction can also occur in less polar solvents due to their incompatible property with the fiber catalysts, which can compel the polar reactants to accumulate on the fiber surface with strong polar microenvironment. Highlights • Two types of microenvironment were constructed on the surface of polyacrylonitrile fiber. • Hydrogen bond has a synergistic catalytic effect with the immobilized basic group in most solvents. • The polar microenvironment on the surface of fiber catalyst can gather reactant in less polar solvents. [ABSTRACT FROM AUTHOR]

A series of reusable and tunable polyacrylonitrile fiber supported catalysts that make use of the cooperative interplay between N -heterocyclic carbene (NHC) Au(III) and amino groups have been developed for synthesis of secondary propargylamines. The yield using immobilized NHC-Au(III) as catalyst is twice as much as that of its small molecule counterpart. Moreover, implementation of a flow system with polyacrylonitrile fiber supported NHC-Au(III) as catalyst leads to a short retention time of 3.3 min and an efficient productivity of 27 mmol/h. The highly catalytic activity of this catalyst is ascribed to the unique hydrophilic microenvironment consisting of NHC-Au(III), -NH 2 and -CN groups in the surface of fiber catalyst. In this microenvironment, the adjacent NHC - Au(III) and amino groups promote the formation of gold-acetylide complex cooperatively with turnover numbers (TON) up to 5200. [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 novel phosphinic acid functionalized polyacrylonitrile fiber (PAN APC F) was prepared and its adsorption properties were investigated. The PAN APC F shows excellent selectivity and efficiency for Hg 2+ in the presence of other common metal ions, viz. Pb 2+ , Cd 2+ , Ag + , Zn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Ca 2+ , Mg 2+ . Adsorption kinetics studies show that PAN APC F quickly captures Hg 2+ and achieves equilibrium within 3 h. In addition, PAN APC F is effective over a wide range of pH values (from 3 to 11). The maximum adsorption capacity for Hg 2+ as calculated by a Langmuir isotherm model was 434 mg g −1 . PAN APC F could also efficiently remove Hg 2+ from practical wastewater and the concentration of Hg 2+ could be decreased as low as 27 ppb, which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China. Furthermore, the PAN APC F can be used to remove Hg 2+ from a flow process with a 99% removal efficiency even after ten cycles. Finally, XPS analysis proved that the P O/P OH and –NH– functional groups play a major role in the adsorption mechanism. [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]

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]

Abstract: A reusable chelating fiber containing polyamino–polycarboxylic acid ligands was prepared via the stepwise modification of polyacrylonitrile fiber with diethylenetriamine and chloroacetic acid. The amination and carboxylmethylation conditions were optimized, and the modified fiber was characterized by elemental analysis, XRD, SEM and FTIR. For Cd2+ in water, this chelating fiber has prominent adsorption abilities such as low adsorption limitation (0.001mg/L), high adsorption capacity (1.34mmol/g) and fast response speed (half-saturation adsorption time less than 0.5min based on 1mg/mL Cd2+). The effectiveness of this chelating fiber has been proved by using it to treat actual sewage water, where the concentration of Cd2+ was reduced from 0.540 to below 0.001mg/L. This level easily meets drinking water standards (0.003mg/L) issued by the World Health Organization. Moreover, this chelating fiber is also very effective at treating other metal ions such as Cu2+, Ca2+, Zn2+, Mg2+, Pb2+, Ni2+, Ag+ and Hg2+. [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]