Expansion of mesopores and concomitant incorporation of metal species into mesoporous silica particles was achieved through the hydrothermal treatment of monodispersed mesoporous silica spheres in an aqueous metal salt solution. Mesopore size was increased to 24 nm from 2.2 nm while retaining monodispersed spherical shape. Surprisingly, hollow spheres were produced when Mg salt was used. Incorporation of metal species led to drastic improvement in adsorption performance. The amount of Rhodamine B adsorbed was increased by 27 times.