Green heterogeneous nickel–chromium oxide catalyst for solvent-free, room-temperature Knoevenagel condensation reaction

This paper discusses synthesizing green, recyclable, heterogeneous nickel–chromium oxide (NiCr₂O₄) catalyst and its application in solvent-free, room-temperature Knoevenagel condensation reaction. Nickel–chromium oxides (Ni–Cr oxides) were prepared using the coprecipitation method in various proportions, such as 2:1, 1:1, and 1:2 ratios. The synthesized catalysts were characterized using X-ray diffraction, SEM-EDX, and BET-surface area analysis. The synthesized catalysts were employed as heterogeneous catalysts in the Knoevenagel condensation model reaction of 4-chlorobenzaldehyde and malononitrile under room temperature, solvent-free grinding reaction conditions, and the results were compared. This paper will discuss the most suitable catalyst and its possible mechanism.