Synthesis and characterization of rhodium oxide nanoparticles in mesoporous MCM-41

Rhodium-containing MCM-41 mesoporous molecular sieves (RhMlCM-41) were synt hesized by adding RhCl3 . 3H(2)O to a mixed silicate-surfactant gel prior t o hydrothermal synthesis. The obtained Rh-MCM-41 samples were characterized by XRD, N-2 adsorption, TEM, Si-29 solid-state NMR and XPS. It was found t hat rhodium oxide nanoparticles <3 nm were located in the MCM-41 mesopore c hannels or 6 nm rhodium oxide particles were dispersed in the MCM-41 matric es, depending on the hydrothermal synthesis temperature and the aging condi tions. The unit eel and pore wall thickness of Rh-MCM-41 synthesized at 423 K were 5.71 and 2.31 nm, respectively, which were larger than those of the corresponding pure Si-MCM-41. The increase in the pore wall thickness may be due to enhancement of cross-linking of =Si-OH in the silicate gel by the presence of Rh ions.