Palladium nanoparticles in vinylimidazolium-based polymers and poly(ionic liquid)s (PIL)s have been synthesized, systematically characterized, and preliminarily tested in the selective hydrogenation of p-chloronitrobenzene to p-chloroaniline. In both nonionic polymers and PILs the palladium nanoparticles were found to be extremely small (below 2 nm) and hardly detectable by means of transmission electron microscopy (TEM) and X-ray powder diffraction (XRPD), but they have ben successfully detected by Fourier transform infrared (FT-IR) spectroscopy of adsorbed CO, which indicated that the available metal surface was approximately the same, as well as the types of exposed sites. In nonionic polymers palladium nanoparticles are stabilized mainly by the interaction with the nitrogen atoms of the imidazole ring, which act as electron donors. In contrast, in absence of available nitrogen species inside PILs, palladium nanoparticles are mainly stabilized by the iodide anions, which determine important electronic effects at the palladium surface. PILs/Pd samples were tested in the selective reduction of p-chloronitrobenzene to p-chloroaniline, under remarkably mild conditions (room temperature, absence: of solvents, gaseous H-2, below 1 atm). The reaction was followed by FT-IR Spectroscopy in operando. All the PILs/Pd samples display an excellent chemoselectivity, whereas nonionic polymers/Pd samples are riot selective. Since the morphology and size of the palladium nanoparticles is the same in all the catalysts, it is concluded that the driving-force for chemoselectivity is the tonicity of the environment provided by the PIL scaffolds.

Spectroscopic study on the surface properties and catalytic performances of palladium nanoparticles in poly(ionic liquid)s

DANI, ALESSANDRO;CROCELLA', VALENTINA;MADDALENA, LORENZA;BAROLO, CLAUDIA;BORDIGA, Silvia;GROPPO, Elena Clara
2016-01-01

Abstract

Palladium nanoparticles in vinylimidazolium-based polymers and poly(ionic liquid)s (PIL)s have been synthesized, systematically characterized, and preliminarily tested in the selective hydrogenation of p-chloronitrobenzene to p-chloroaniline. In both nonionic polymers and PILs the palladium nanoparticles were found to be extremely small (below 2 nm) and hardly detectable by means of transmission electron microscopy (TEM) and X-ray powder diffraction (XRPD), but they have ben successfully detected by Fourier transform infrared (FT-IR) spectroscopy of adsorbed CO, which indicated that the available metal surface was approximately the same, as well as the types of exposed sites. In nonionic polymers palladium nanoparticles are stabilized mainly by the interaction with the nitrogen atoms of the imidazole ring, which act as electron donors. In contrast, in absence of available nitrogen species inside PILs, palladium nanoparticles are mainly stabilized by the iodide anions, which determine important electronic effects at the palladium surface. PILs/Pd samples were tested in the selective reduction of p-chloronitrobenzene to p-chloroaniline, under remarkably mild conditions (room temperature, absence: of solvents, gaseous H-2, below 1 atm). The reaction was followed by FT-IR Spectroscopy in operando. All the PILs/Pd samples display an excellent chemoselectivity, whereas nonionic polymers/Pd samples are riot selective. Since the morphology and size of the palladium nanoparticles is the same in all the catalysts, it is concluded that the driving-force for chemoselectivity is the tonicity of the environment provided by the PIL scaffolds.
2016
120
3
1683
1692
http://pubs.acs.org/journal/jpccck
TRANSITION-METAL COORDINATION; IMIDAZOLIUM IONIC LIQUIDS; BLOCK-COPOLYMER MICELLES; PD NANOPARTICLES; PARTICLE-SIZE; O-CHLORONITROBENZENE; COLLOIDAL CLUSTERS; ALUMINA CATALYSTS; MODEL CATALYSTS; CARBON-MONOXIDE
Dani, A.; Crocellà, V.; Maddalena, L.; Barolo, C.; Bordiga, S.; Groppo, E
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1570317
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