Novel molybdenum–cerium based heterogeneous catalysts for efficient oxidative coupling of benzylamines under eco-friendly conditions

This work demonstrates that MoO x /CeO 2 –ZrO 2 solid acid acts as a promising catalyst in the solvent-free oxidative-coupling of benzylamine into dibenzylimine with O 2 as the oxidant. The benzylamine conversions were found to be ~27, 51, 74, and 99 % for CeO 2 , CeO 2 –ZrO 2 , MoO x /CeO 2 , and MoO x /CeO 2 –ZrO 2 catalysts, respectively. The MoO x /CeO 2 –ZrO 2 catalyst also efficiently converts various substituted- and secondary-benzylamines under solvent-free conditions with O 2 resulting in moderate to excellent yields. Remarkably, a high selectivity of ~99.6–99.9 % towards the dibenzylimine product was found for all reaction conditions. The outstanding performance of MoO x /CeO 2 –ZrO 2 catalyst was attributed to high specific surface area, improved structural defects, and superior acid properties. Graphical Abstract The MoO x /CeO 2 –ZrO 2 catalyst show an outstanding performance in the oxidation of benzylamine and its derivatives, which is attributed to abundant acidic sites, large number of oxygen vacancies, and superior BET surface area.