Coupling reactions of aromatic halides with palladium catalyst immobilized on poly(vinyl alcohol) nanofiber mats

Abstract

Nanoporous poly(vinyl alcohol) (PVA) nanofiber mats prepared by means of electrospinning have been used for the immobilization of palladium catalyst. Thermal treatment of the palladium-loaded PVA nanofiber mats results in the cross-linking of the matrix PVA molecules as well as the reduction of the divalent palladium (Pd 2+) into zerovalent palladium (Pd 0) species. The palladium oxidation states were examined by X-ray photoelectron spectroscopic (XPS) analysis. The PVA nanofiber morphology was characterized by scanning electron microscopy (SEM). The catalytic activity and recyclability of the prepared heterogeneous palladium catalysts have been evaluated for the Ullmann, Heck–Mizoroki and Sonogashira coupling reactions of aromatic halides. The large structure of the Pd/PVA nanofiber mats can greatly facilitate its separation and recycling, and the high catalytic activity and stability of the prepared Pd/PVA nanofiber mats have been attributed to the chelation of palladium species with the abundant hydroxyl functional groups on the PVA matrix surface area.