The temperature-programmed decarbonylation process of Mo(CO)(6) in NaY zeolite was studied by means of a time-resolved energy-dispersive XAFS method. The XANES analysis demonstrated that the decarbonylation proceeded by two successive steps via a stable intermediate which existed between 440 and 490 K, The curve fitting analysis of the EXAFS data revealed that the intermediate was a molybdenum monomer subcarbonyl species Mo(CO)(3)(O-L)(3) coordinated by three CO ligands and three oxygen atoms of zeolite framework (O-L). Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that the DXAFS technique is a powerful method to study the dynamic behavior of the Mo carbonyl species during decarbonylation process.