MCM-41 based materials were prepared with immobilized Mo-II and Mo-VI active sites based on [Mol(2)(CO)(3)] and [MoO2Cl2] cores, respectively, using a 2-aminopyridine glycidyloxypropyl derivative as anchoring ligand. Suitable characterization by powder X-ray diffraction, FTIR and, C-13 and Si-29 solid state NMR spectroscopy was accomplished. All new materials were successfully used in photodegradation experiments of rhodamine B under aerobic conditions. Control experiments using neat MCM-41 and direct photolysis of rhodamine B were also carried out. All experiments were run without any external source of oxygen other than air. Photocatalytic results show that the presence of Mo and its oxidation state is not innocent in this process. In addition, Mo catalysts act most probably by quenching rhodamine B excited state leading to extended degradation of the dye, through secondary photochemistry, beyond a simple de-ethylation process. Density functional theory (DFT) results corroborate with this showing that when rhodamine B is in excited state the xanthene moiety bond orders change. (C) 2011 Elsevier B.V. All rights reserved.