Tuning the Catalytic Activity of Tertiary-Amine Functionalized Polyacrylonitrile Fibers by Adjusting the Surface Microenvironment

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 (PAN(BT)F) shows much higher catalytic activity than that modified by hydrophilic ethanola-mine groups. PAN(BT)F 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 PAN(BT)F. 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 PAN(BT)F in industrial production.