α- and β-CoNi binary hydroxides nanostructures: Synthesis, characterization, and application as heterogeneous catalysts

The aim of this study is to show that α- and β-CoNi binary hydroxides nanostructures can be used as heterogeneous catalysts in the oxidation of benzyl alcohol, N-formylation of aniline, and the Claisen–Schmidt condensation. The catalysts were synthesized by hydrothermal method and characterized by XRD, FE-SEM/EDX, FT-IR, TGA, UV–vis and N₂ adsorption-desorption techniques. The α-phase is similar to layered double hydroxide (LDH), while β-phase is isostructural with brucite. In all of the three reactions, the conversion enhanced by increasing the amount of catalysts from 10 to 30 mg, and the catalytic activity of α-phase was better than β-phase. In benzyl alcohol oxidation, the best conversion for α- and β-phases was 90% and 80%, respectively, under solvent-free conditions. In N-formylation, the best yield for both catalysts was obtained 95% in solvent-free conditions. However, the time required for α-phase to reach this amount was a quarter of that for β-phase. For the Claisen–Schmidt condensation, the best yield was obtained at 90 °C, which was 70% and 50% for α- and β-CoNi binary hydroxides, respectively. Both catalysts were stable and subsequent to each step of recovery and reuse, no significant loss in activity was observed.