Sonochemically induced cube-shaped NiFe2O4 nanoparticle-catalyzed selective oxidation of benzyl alcohol to benzaldehyde

Abstract

Selective oxidation of benzyl alcohol to benzaldehyde is one of the vital reactions because of the commercial application of benzaldehyde in various chemical and pharmaceutical industries. This work investigates a gentler method for creating NiFe₂O₄ nanoparticles (NPs) by a co-precipitation method combined with hydrothermal ageing in the presence of poly(ethylene glycol) (PEG) of different molecular weights. The investigation findings reveal the formation of well-crystalline cube-shaped and a mixture of spherical and cube-shaped particles depending on the concentration of the additive. The formed particles are magnetically ordered exhibiting superparamagnetic behaviour at room temperature with saturation magnetization (M_s) values ranging from 41.0 to 43.0 emu g⁻¹. The as-prepared NiFe₂O₄ NPs can selectively catalyze the oxidation of benzyl alcohol to benzaldehyde at room temperature under sonochemical conditions in the presence of tert-butyl hydroperoxide. Under the optimized conditions, 90% of benzaldehyde with 100% selectivity in 2.0 h at room temperature (25–30 °C) is recorded. The versatility of the current protocol has been extended to a variety of substituted benzyl alcohols with good to excellent performance under the optimized reaction conditions. The NiFe₂O₄ NPs are magnetically separable and can be reused for up to seven cycles without losing their catalytic activity.