Tuning the catalytic performance of a Cu supported silica modified γ-Al2O3 nanocatalyst via cobalt-doping for A3-coupling

Abstract

Tuning the catalytic activity and selectivity of a heterogeneous transition nano-metal catalyst by the controlled incorporation of a foreign entity (dopant) into its structure is of paramount importance, although a great challenge. Further, understanding and revealing the mechanistic insight behind the promotional role of dopants remains as another formidable task in designing efficient doped heterogeneous catalysts with enhanced catalytic performance. In the present study, a Co²⁺-doped Cu supported silica modified γ-Al₂O₃ nanocomposite [Co²⁺-Cu@SA(7.5)-600] with a fibrous morphology, large specific surface area, high crystallinity and thermal stability was synthesized using an efficient and sustainable procedure and then its catalytic activity was evaluated for the synthesis of a wide variety of propargylamines via A³-coupling. Comparative analysis revealed the doped catalyst to be more efficient than its corresponding undoped counterpart and catalysts from earlier reported studies. Focus was laid down on exploring the exact reason behind the promotional role of the dopant. XPS spectra of the Co²⁺-doped and undoped Cu catalysts indicated electronic tuning in the doped Cu catalyst as compared to its undoped counterpart, i.e. electronic synergism between Co²⁺-ions and Cu NPs, which forms the basis of the enhanced catalytic performance of the doped catalyst, as clearly supported by a plausible mechanism. Hence, by providing mechanistic insights into the promotional role of dopant, our study offers a competent strategy for designing efficient heterogeneous catalysts with enhanced catalytic performances.