In this study, novel bi-functional Fe3O4/mesoporous silica core/shell nanoparticles (FMSNs) modified by thiol groups (-SH) on their outer surfaces have been successfully synthesized through outside-in functionalization process, and then can be served as the three-dimensional porous supporting materials to complex with platinum ions in the mesoporous channels, where high-density amino groups (-NH2) are grafted as the binding sites for chelating metal precursors in the inner of mesopores. Highly dispersed Pt nanoparticles are facilely generated and immobilized into the channel surfaces of FMSNs by an in-situ reduction using NaBH4 as the reducing agent. The special FMSNs possess high Pt loading capacity (similar to 10.38%), and can be acted as active heterogeneous catalysts for the reduction of toxic Cr(VI) to Cr(III) by using formic acid as the model reducing agent. The Pt-loaded FMSN catalysts can be facilely separated and collected by applying an outer magnetic field, and the catalysts can be reused for five times successively with excellent performance. We believe that the composites have large potential in the removal of Cr(VI) contamination from industrial waste-water in the future. (C) 2017 Published by Elsevier B.V.