Publisher Summary Transition metal carbonyls grafted on porous materials are of special interest in catalysis, separation technology and materials science, for example the periodic mesoporous structure of MCM-41. The use of metal carbonyls as active metal precursor allows the possible control of metal location and specific clustering into the mesoporous channels of MCM-41, thus offering a better control of activity and selectivity for potential catalytic reactions In turn, these materials could be used as heterogeneous catalysts for decarbonylation, bond substitution, and other catalytic reactions that could be sensitive to active species attached on the surface groups of the porous materials. The examination of these novel materials should provide also a route for obtaining highly dispersed low valence metals. At present, chemical vapor deposition (CVD) is used for anchoring metal carbonyls on oxide type surfaces, but in most of these cases a weak interaction between carbonyl complexes and surface groups occurs. This chapter investigates the synthesis of siliceous MCM-41 grafted with transition metal carbonyls. The transition metal carbonyls were grafted over MCM-41 siliceous mesoporous materials—Cr(CO)6, Mn2(CO)10, and Co2(CO)8. These species were grafted using ultraviolet (UV) radiation for generating coordinated non saturated species; ultrasound was applied to provoke further interaction between Fe2(CO)9 and MCM-41. The surface species were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and thermal analysis.