Dendritic SBA-15 supported HRh(CO)(PPh3)(3) catalysts were designed for liquid-phase hydrol styrene. The silanolls outside SBA-15 channels were passivated so that HRh(CO)(PPh3)(3) complexes could be anchored mostly inside the SBA-15 channels. After passivation, PAMAM (polyamdoamine) dendrimers up to second generation were then grown inside the SBA-15 channels. Both pore size and dendrimer generation were found to influence the performance of catalysts for styrene hydroformylation, and the second-generation PAIVIAM was found to be optimal for these passivated dendritic SBA-15-supported rhodium catalysts. To study the effect of tethering HRh(CO)(PPh3)(3) inside and outside SBA-15 mesopore we also studied SBA-15-supported catalyst analogs with no passivation of external silanols. The channels, passivated SBA-15 supported rhodium catalysts demonstrated an increase in catalytic activity and stability when the generation of supported dendrimer was increased from zeroth to second generation. (c) 2008 Published by Elsevier Inc.