Porous chitosan-derived activated N-doped carbon-supported Pd nanoparticles encaged in Al, Fe pillared montmorillonite as novel heterogeneous catalysts

Abstract

Novel pillared montmorillonite encaging porous chitosan derived activated N-doped carbon-supported Pd nanoparticles catalyst (Pd@Al, Fe-Mt/N-C) was synthesized by ion-exchange of the chitosan/Pd precursors into the layered-nanospaces of Al, Fe-pillared montmorillonite and subsequent confinement carbonization. N2 adsorption-desorption study indicated that the resulting nanocomposites have rich mesoporous structures. Effective encagement and in-situ reduction of Pd species led to a decrease in surface area and N2 adsorption, respectively. TEM images of the prepared Pd@Al, Fe-Mt/N-C showed that most of the Pd species with a size of 1–3 nm were well dispersed in the interlayer spaces of the pillared montmorillonite. The catalysts showed high catalytic efficiency for the Sonogashira reactions of aryl iodides or bromides with terminal aryl alkynes, and can be recycled 20 runs with no significant loss of activities. The unique encagement of the porous carbon-supported metal catalysts in the layered nanospaces of pillared montmorillonite was further elucidated by the positron annihilation spectroscopy analysis and other structural characterization methods. This layered-nanospace confinement strategy achieves a perfect combination of the advantages of activated carbon and montmorillonite as metal nanoparticle carrier.