Binary copper and iron oxides immobilized on silica-layered magnetite as a new reusable heterogeneous nanostructure catalyst for the Knoevenagel condensation in water

Abstract

In this study, a novel heterogeneous and reusable nanostructure catalyst was synthesized through the immobilization of bimetallic Cu–Fe mixed oxides on silica-layered magnetite. The prepared nanomagnetic Fe3O4@SiO2@CuO–Fe2O3 was characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, Brunauer–Emmett–Teller analysis, thermogravimetric analysis, differential thermal gravity, a vibration sample magnetometer, transmission electron microscopy and inductively coupled plasma optical emission spectroscopy. The catalytic activity of this mesoporous nanocomposite was studied in the Knoevenagel condensation of aromatic aldehydes and malononitrile in water to afford benzylidenemalononitriles in high to excellent yields. The nanocatalyst was able to be recycled five times without a significant loss in catalytic activity. This nanostructure catalyst allows for mild reaction conditions and acceptable reaction times, while delivering the desired products in high purity and yield without the use of dangerous organic solvents.