Highly dispersed metal nanoparticles were immobilized in the pores of a metal-organic framework (MOF), MIL-101, using a double solvents method. The resulting composites were investigated in the reduction of Cr(VI) to Cr(III) using formic acid, showing that the Pt and Pd catalysts were active with the Pt nanoparticles immobilized in MOF exhibiting the best performance.