Pd–ZnO nanowire arrays as recyclable catalysts for 4-nitrophenol reduction and Suzuki coupling reactions

Abstract

In this work, we report a facile approach for the preparation of Pd nanoparticle–ZnO nanowire arrays followed by demonstrating their use as recyclable catalyst for reactions under different conditions. The facile synthesis largely relies on a spontaneous reduction of PdCl₄²⁻ at the surface of oriented ZnO nanowires grown on a Zn foil. This is due to a combination of the strongly reducing ability of Zn foil and the semiconducting nature of ZnO nanowires. At room temperature and under a weak alkaline condition, the as-prepared Pd nanoparticle–ZnO nanowire arrays show a catalytic activity factor up to 76.6 s⁻¹ g⁻¹ in the reduction of 4-nitrophenol and no obvious decreases in the catalytic activity even after use of 10 times. Meanwhile, the as-prepared Pd nanoparticle–ZnO nanowire arrays exhibit extraordinary catalytic activity toward Suzuki and carbonylative Suzuki reactions at a higher temperature under a stronger alkaline condition. The outstanding performance of the hybrid nanowire arrays is mainly originated from the small size of the Pd nanoparticles (∼2–4 nm) with clean surfaces, as well as a strong affinity between the Pd nanoparticles and ZnO nanowires, leading to marginable catalyst loss and aggregation. Considering the multiple choices of both noble metal nanocatalyst and transition metal oxide nanowire array, we expect noble metal nanoparticle-transition metal oxide nanowire arrays to be emerged as a new class of recyclable catalysts attractive for diverse organic reactions to develop pharmaceuticals, natural products and advanced functional materials.