Hierarchically assembled palladium catalysts: preparation of heterogeneous biocatalysts via a facial route for the Heck coupling reaction

The scientific community has long been intrigued by the potential practical applications of metal nanoparticles. In this research, we developed cost-effective and easily accessible palladium nanoparticle (Pd-NP)-supported biocatalysts using natural materials. Our main challenge was to ensure an even distribution of Pd-NPs on the bacterial surface while preventing their detachment during the reaction. We successfully addressed this challenge by employing a suitable synthesis method and covering the Pd-NP-coated bacteria with sericin. In our approach, we synthesized Pd-NPs using an in-situ method. In brief, we adsorbed Pd(II) ions onto the bacterial surface and then reduced them using sodium borohydride. Subsequently, we used a sericin solution to enhance the catalytic system’s resistance to leaching and mechanical forces (such as shaking and drying). We thoroughly characterized the morphology and structure of the heterogeneous biocatalysts prepared using FTIR, TGA, EDX, SEM, XRD, and TEM techniques. The catalytic efficiency of the bacteria-Pd-sericin nano-biocomposite was evaluated in the Heck coupling reaction. Our biocatalyst demonstrated high catalytic activity, rapid reaction times, and exceptional reusability, remaining active for up to four successive reaction cycles.