RhNPs supported on N -functionalized mesoporous silica: effect on catalyst stabilization and catalytic activity

• Published in: Dalton transactions : an international journal of inorganic chemistry 2021-03, Vol.50 (9), p.3289-3298
• Main Authors: Pulido-Díaz, Israel T, Serrano-Maldonado, Alejandro, López-Suárez, Carlos César, Méndez-Ocampo, Pedro A, Portales-Martínez, Benjamín, Gutiérrez-Alejandre, Aída, Salas-Martin, Karla P, Guerrero-Ríos, Itzel
• Format: Article
• Language: English
• Subjects: Acetophenone; Aromatic compounds; Carbonyls; Catalysts; Catalytic activity; Hydrogenation; Morpholine; Nanoparticles; Nicotinamide; NMR; Nuclear magnetic resonance; Rhodium; Silicon dioxide; Size distribution; Substrates; X ray photoelectron spectroscopy
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d0dt04213g

Amine and nicotinamide groups grafted on ordered mesoporous silica (OMS) were investigated as stabilizers for RhNPs used as catalysts in the hydrogenation of several substrates, including carbonyl and aryl groups. Supported RhNPs on functionalized OMS were prepared by controlled decomposition of an organometallic precursor of rhodium under dihydrogen pressure. The resulting materials were characterized thoroughly by spectroscopic and physical techniques (FTIR, TGA, BET, SEM, TEM, EDX, XPS) to confirm the formation of spherical rhodium nanoparticles with a narrow size distribution supported on the silica surface. The use of nicotinamide functionalized OMS as a support afforded small RhNPs (2.3 ± 0.3 nm), and their size and shape were maintained after the catalyzed acetophenone hydrogenation. In contrast, amine-functionalized OMS formed RhNP aggregates after the catalytic reaction. The supported RhNPs could selectively reduce alkenyl, carbonyl, aryl and heteroaryl groups and were active in the reductive amination of phenol and morpholine, using a low concentration of the precious metal (0.07-0.18 mol%).