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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]

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 polyacrylonitrile fiber-supported Brønsted acid catalyst has been developed and verified to efficiently (high yield, 10 cycles) mediate Biginelli reactions in ethanol, Pechmann condensations in toluene, Friedel-Crafts alkylations of indoles in water and conversion of fructose in dimethyl sulfoxide (DMSO) and mixed-aqueous system. [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]

• 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]