We have synthesized a series of catalysts for epoxidation of styrene by immobilizing salicylaldimine transition metal (copper, manganese, and cobalt) complexes on mesoporous silica nanoparticles (MSNs) with diameters of 120-150 nm. The prepared catalysts are characterized by infrared (IR) spectra, thermal gravimetric analyses (TGA), inductively coupled plasma (ICP), CHN elemental analysis, nitrogen adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). These catalysts possess excellent catalytic efficiency in epoxidation of styrene when using tert-BuOOH (TBHP) as oxidant. Styrene shows a high conversion (similar to 99%) as well as epoxide selectivity (similar to 80%) over Cu-MSN catalysts, and high conversion (similar to 99%) and moderate epoxide selectivity (similar to 65%) over Mn-MSN and Co-MSN catalysts. The recycling experiment results indicate that these catalysts maintain catalytic activity even after being used for three cycles. Our results indicate that MSNs can serve as better catalyst supports. (C) 2010 Elsevier Inc. All rights reserved.