Preparation and Structure Analysis of Co−Mo Binary Sulfide Clusters Encapsulated in an NaY Zeolite

Abstract

In our previous study, it was proposed that thermally stable intrazeolite Co−Mo binary sulfide clusters were synthesized using as precursors Mo(CO)6 and Co(CO)3NO adsorbed in the pores of an NaY zeolite. In the present study, the formation of Co−Mo binary sulfide clusters is shown by Co 2p X-ray photoelectron spectroscopy (XPS) and Mo and Co K-edge extended X-ray absorption fine structure (EXAFS) techniques. It is concluded on the basis of XPS and X-ray fluorescence (XRF) analyses that the composition of the clusters is Co2Mo2S6. It is strongly suggested by Mo and Co K-edge EXAFS analysis that the structure of Co2Mo2S6 clusters is of thiocubane type. The thiocubane structure is rationalized by theoretical calculations using a density functional method. It is concluded that the intrazeolite Co−Mo binary sulfide clusters Co2Mo2S6, possessing a thiocubane structure thermally stabilized by interactions with the framework of the host zeolite, are synthesized by using Mo(CO)6 and Co(CO)3NO. Analogies in the synthesis reactions of Co−Mo thiocubane clusters are suggested between homogeneous reaction systems and the present zeolite pore system.