Copper aluminum mixed oxide (CuAl MO) catalyst: A green approach for the one-pot synthesis of imines under solvent-free conditions

• A copper aluminum mixed oxide (CuAl MO) catalyst has been synthesized using activated carbon as the template.
• The catalyst shows excellent activity for direct imine formation by oxidative coupling of alcohols and amines under solvent free conditions using air as the oxidant.
• The catalyst exhibits high stability and recyclability.
• The presence of higher number of Lewis acidic sites, surface oxygen availability and facile reversibility of oxygen readsorption on the surface account for the superior activity and high durability of the catalyst.

Activated carbon templated Copper Aluminum mixed oxide (CuAl MO) catalysts have been synthesized and studied for direct imine formation by oxidative coupling of alcohols and amines under solvent free conditions. Among the catalysts, CuAl MO20%C (catalyst synthesized by adding 20% activated carbon) shows the best activity and selectivity for this reaction. Here, air is used as the oxidant which is considered as the most economical and green oxidant among different oxidizing agents. Pyridine adsorption results confirmed that the presence of higher number of Lewis acidic sites enhances the catalytic activity of the material. Various alcohol and amine substrates were readily converted into the corresponding imines in good to excellent yields. According to catalytic activity studies and TG-MS data, surface oxygen availability and facile reversibility of oxygen readsorption on the surface account for the superior activity and high durability of the CuAl MO20%C catalyst. The regenerated catalyst showed 92% conversion with 100% selectivity even after the 4th reuse.

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