Pd nanoparticles encapsulated into mesoporous ionic copolymer: Efficient and recyclable catalyst for the oxidation of benzyl alcohol with O₂ balloon in water

A series of functional cross-linked mesoporous poly(ionic liquid)s (MPILs) were prepared through the free radical copolymerization of divinylbenzene (DVB) and imidazolium salts based ionic liquids tethered with different groups (-COOH, C₄H₉, -CN and -NH₂). These MPILs were applied as supports to prepare immobilized palladium (Pd) nanoparticles (NPs) through ion exchanging with sodium tetrachloropalladate(II) (Na₂PdCl₄) and successive reduction by sodium borohydride (NaBH₄). Highly uniform and narrow dispersed Pd NPs attained on the carboxyl modified MPIL with large surface area and high ionic density. The obtained materials acted as an efficient and stable recycling heterogeneous catalyst for the atmospheric pressure oxidation of benzyl alcohol to benzaldehyde by using O₂ as the oxidant and water as the sole solvent at low temperature (90 °C). The special ionic framework with -COOH group plays a major role in the formation and stabilization of ultrafine Pd NPs. This work indicates that controlling the textural properties of ionic copolymers serves as a facile and efficient way to fabricate immobilized stable metal NPs.