The controlled gas-phase loading of a metal–organic framework (MOF) to generate iridium nanoparticles is described. The key is the use of an Ir complex, which was small enough to fit through the pore apertures of the MOF, stable enough to be vaporized and labile enough to be reduced inside the pores of the MOF. Homogenously distributed, nanometer-sized and highly crystalline iridium nanoparticles, located inside the pores of the still intact host matrix of MIL-101 (Cr) could be generated. The material was characterized using electron microscopy, X-ray diffraction, elemental analysis and nitrogen physisorption techniques. Initial catalytic tests showed a high activity in olefin hydrogenation.