The CuFe 2 O 4 @SiO 2 @ZrO 2 /SO 4 2- /Cu nanoparticles: an efficient magnetically recyclable multifunctional Lewis/Brønsted acid nanocatalyst for the ligand- and Pd-free Sonogashira cross-coupling reaction in water.

Herein, the synthesis and application of copper-incorporated sulfated zirconium oxide supported on CuFe 2 O 4 NPs (CuFe 2 O 4 @SiO 2 @ZrO 2 /SO 4 2- /Cu NPs) as a novel Lewis/Brønsted acid nanocatalyst were studied for the Sonogashira C-C cross-coupling reaction. The fabricated CuFe 2 O 4 @SiO 2 @ZrO 2 /SO 4 2- /Cu catalyst exhibited efficient activity for a large variety of aryl iodides/bromides and, most importantly, aryl chlorides in water and in the presence of NaOH as a base in short reaction times. The catalyst was fully characterized by FTIR, TG-DTG, VSM, XRD, EDX, FE-SEM and TEM analyses. A synergetic effect could be considered to have arisen from the various Lewis acid and Brønsted acid sites present in the catalyst. The efficient incorporation of copper into zirconia provided a robust highly stable hybrid, which prevented any metal leaching, whether from the magnetite moiety and/or Cu sites in the reaction mixture. Moreover, the catalyst was successfully recovered from the mixture by a simple external magnet and reused for at least 9 consecutive runs. Zero metal leaching, stability, consistency with a variety of substrates, fast performance, cost-effectiveness, environmental friendliness, and preparation with accessible and cheap materials are some of the advantages and highlights of the current protocol.