Magnetic PdOx/NiFe2O4 hybrid nanofibers with high catalysis and reusability for Suzuki coupling reactions

Abstract

Pd-based catalysts with high activity and recoverability are desirable for Suzuki coupling reactions which represent an important strategy for constructing carbon-carbon bonds in organic synthesis. Herein, a magnetic PdOx/NiFe2O4 NFs catalyst consisting of PdOx nanoparticles (NPs) and NiFe2O4 nanofibers (NFs) is synthesized by an electrospinning-calcination process. The microstructures and chemical compositions of PdOx/NiFe2O4 NFs catalyst are well characterized. The optimized PdOx/NiFe2O4 NFs exhibits high catalysis toward Suzuki coupling reactions under mild conditions, benefiting from the special electronic state of Pdδ+ (0 < δ < 2) active sites and the porous nanofiber structure of NiFe2O4 support. The turnover frequencies (TOFs) for the reactions of iodo-, bromo- and chloro-benzene over the PdOx/NiFe2O4 NFs catalyst reach up to 2064.79, 1366.74 and 215.28 h−1, respectively, far exceeding those over the commercial Pd/C catalyst. The kinetic studies demonstrate that the PdOx/NiFe2O4 NFs catalyst is more efficient to reduce the activation energy of Suzuki coupling reaction, which can be attributed to the superiority of Pdδ+ species in both charge-donating and charge-accepting steps of the reactions. Moreover, the PdOx/NiFe2O4 NFs catalyst can be facilely separated and recycled in a long-term catalytic reaction owing to its distinct magnetic feature and good structural stability. This work affords a facile approach for the synthesis of heterogeneous catalyst with tunable compositions and porous structures as well as an attractive catalyst with superior catalytic activity, high stability and reusability.