Recyclable Polymer-supported Nanometal Catalysts in Water

Two types of polymer-supported nanometal catalysts with high catalytic activity and recyclability in water have been developed. One catalyst was composed of linear polystyrene-stabilized metal nanoparticles (PS-MtNPs). A palladium catalyst (PS-PdONPs) was prepared in water by the thermal decomposition of Pd(OAc)2 in the presence of polystyrene. The degree of immobilization of Pd, but not the size of the Pd nanoparticles, was dependent on the molecular weight and cross-linking of the polystyrene. The PS-PdONPs exhibited high catalytic activity for Suzuki, Heck, and Sonogashira coupling reactions in water and they could be recycled without loss of activity. Linear polystyrene was also suitable as a stabilizer for in situ generated PdNPs and PtNPs. The second catalyst was a polyion complex that was composed of poly[4-chloromethylstyrene-co-(4-vinylbenzyl)tributylammonium chloride] and poly(acrylic acid)-stabilized PdNPs (PIC-PdNPs). Aggregation and redispersion of PIC-PdNPs were easily controlled by adjusting the pH value of the solution.