The TPPTS-Rh complex [TPPTS = trisodium salt of tri-(m-sulfophenyl)-phosphine, P(m-C6H4SO3Na)(3)], which was dissolved in the ionic liquids 1-butyl-3-methyl-imidazolium tetrafluoroborate (BMI• BF4), 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMI-PF6), and 1,1,3,3-tetramethylguanidinium lactate (TMGL), was immobilized on MCM-41. The resulting supported ionic liquid-phase catalysts (SILPCs) were very active for the hydroformylation of higher olefins. The SILPCs with the regular hexagonal array of MCM-41 were structurally stable before and after the catalytic reaction, as characterized by XRD, N-2 adsorption/desorption, FTIR P-31-NMR, SEM, HRTEM, and TGA-DSC. The obtained SILPCs showed higher catalytic activity, independent of IL type, as compared with their ionic liquid-organic biphasic counterparts and the one with SiO2 as carrier. Such SILPCs could be reused several times without significant loss of activity or selectivity. © 2005 Elsevier Inc. All rights reserved.