Palladium metal nanoparticles have been applied to hydrodechlorination of chlorophenols in contaminated water using H-2 as a clean and sustainable reductant. However, there are two major challenges to widespread technology adoption which are the activity loss caused by nanoparticle aggregation and the difficulty of nanoparticle recovery. In this study, a synthesis of a core-shell structured catalyst with encapsulated Pd nanoparticles has been given and. whose catalytic activity has been tested in hydrodechlorination of chlorophenols under 1 atm H-2 at room temperature. The catalyst material consists of a nonporous silica core decorated with Pd nanoparticles that are further encapsulated within an ordered mesoporous silica shell. Well-defined mesopores (2.4nm) provide a physical barrier to prevent Pd nanoparticle (-10 nm) movement, aggregation and detachment from the support into water. Compared with some supported Pd catalysts such as Pd/AC and Pd/Al2O3, SiO2/Pd@m-SiO(2)exhibits higher catalytic performance. After 5 times of recycling, catalytic activity of SiO2/Pd@m-SiO2 reduces slightly and this result confirms the good recyclability of SiO2/Pd@m-SiO2. The function of the mesoporous shell, preventing aggregation of active nanoparticles, suggests a promising general strategy of using metal nanoparticle catalysts for water purification and related aqueous-phase applications. (C) 2015 Elsevier B.V. All rights reserved.