Pd Nanoparticles Decorated on ZnO/Fe₃O₄ Cores and Doped with Mn²⁺ and Mn³⁺ for Catalytic C–C Coupling, Nitroaromatics Reduction, and the Oxidation of Alcohols and Hydrocarbons

In spite of the enhanced catalytic performances exhibited by the doped transition nano-metal catalysts, understanding and unraveling the mechanistic part behind the promotional nature of dopants remains a challenge. The present work involves a comparative analysis of Mn3+- and Mn2+-doped supported Pd nano-catalysts with undoped counterparts for C–C coupling, reduction, and oxidation. Efforts were made to gain deep insights into the promotional role of dopant ions. X-ray photoelectron spectroscopy spectra of fresh and reused catalysts in case of each organic transformation provided mechanistic insights into the role of dopant ions which has proved helpful in formulating mechanisms where the electronic synergism between dopants and reactant/metal nanoparticles has been depicted. The effect of Mn3+ ions on the electronic environment of aryl halide in case of C–C coupling makes the Mn3+-doped nano-catalyst more efficient, as compared to Mn2+-doped and undoped nano-catalysts. The strong electronic interactions between Mn2+ and Pd make the Mn2+-doped nano-catalyst efficiently active and selective for reduction and oxidation. The present approach provides proper evidence for the changes/interactions that are induced by the introduction of dopants in heterogeneous nano-metal catalysts. Consequently, the underlying synthetic route to design efficient doped heterogeneous transition nano-metal catalysts and a deeper mechanistic view of the promotional role of dopant will prove to be a promising approach in the field of heterogeneous nano-metal catalysis.