Stepwise synthesis and structure analysis of Mo dimers in NaY zeolite

Mo dimers were prepared in the supercage of NaY zeolite by cycles of satura ted adsorption of Mo(CO)(6) at room temperature and subsequent thermal deco mposition at 573 K. The obtained samples were characterized by temperature- programmed desorption, extended X-ray absorption fine structure (EXAFS), X- ray photoelectron spectra, and X-ray fluorescence. Two Mo(CO)(6) molecules per supercage were immobilized in each process. After the thermal decomposi tion of the adsorbed Mo(CO)(6) in the supercage, the resultant Mo(1)/NaY co uld accept two more Mo(CO)(6) molecules per supercage. Mo loading was found to increase linearly by two Mo(CO)(6) molecules in a supercage per one dep osition cycle, and was saturated with eight Mo atoms per supercage after th e four cycles. EXAFS analysis revealed that Mo(II) oxocarbide dimer species [Mo-2(C)(O)(x)] with the Mo-Mo distance of 0.285 nm was formed in the supe rcage by the 573 K thermal decomposition of the adsorbed Mo(CO)(6). The str uctures of Mo oxocarbide dimers were invariant regardless of the Mo loading .