Core-shell iron oxide@cathecol-polymer@palladium/copper nanocomposites as efficient and sustainable catalysts in cross-coupling reactions

Magnetic core-shell Fe2O3@polymer-Pd/Cu nanocomposites (NCs) were developed as efficient and sustainable nanocatalysts for cross-coupling reactions. The designed NCs consisted of three components: i) a magnetic core (Fe2O3 nanoparticle), which allowed the recovery and reuse of the NCs, enhancing thus their attractiveness as green catalysts; ii) a catechol-based polymer coating, chosen because of its strong chelating ability towards metal ions, and its potential to be obtained from biomass (lignin depolymerization); and iii) catalytically active metal nanoparticles (Pd and Cu NPs) immobilized via in situ formation onto the polymeric shell. As-prepared Pd-based NCs successfully catalyzed Suzuki-Miyaura cross-coupling reactions, achieving yields between 87% and 97% in only 20-40 min depending on the aryl halides and boronic acid derivatives. Similarly, Cu-based NCs exhibited a quite good catalytic efficiency (> 80%) in the synthesis of propargylamines via A(3) coUpling reaction of phenylacetylene with various aldehydes and amines. Importantly, these NCs presented a good reusability, without significant decrease in efficiency after several cycles. However, the major advantage of the designed NCs is the lower Pd or Cu content (1.5 wt% and 2.6 wt%, respectively) as compared to most of the reported similar catalysts (between 3 - 6 wt% for Pd and > 5 wt% for Cu), which is a key challenge in view of developing cost-effective and environment-friendly catalysts while maintaining a high efficiency.