Abstract: Zeolite Y encapsulated symmetrical and unsymmetrical Co(II)Salen- type Schiff base complexes with different substituents were prepared by flexible ligand method and characterized by XRD, FTIR, UV- Vis, and thermal analysis. The effects of substituents on encapsulation and catalytic activity of the encapsulated complexes were also investigated. The results indicated that the complexes could be formed and encapsulated in the supercages without affecting the zeolite framework structure. The prepared castalysts exhibited high activity, selectivity, as well as stability in the epoxidation of styrene with molecular oxygen. The highest conversion and selectivity towards styrene oxide could reach 93.2% and 75.6% respectively at 110 ℃ under 0.1 g catalyst, 5 mmol of styrene and oxygen saturated conditions. The recycled catalyst did not show any decrease in catalytic activity and selectivity. Substitution of the aromatic hydrogen atom of the Salen ligand with electron withdrawing group Br decreased the amount of the complex encapsulated in the zeolite cavities, but could improve the catalytic activity of the encapsulated complex. Density functional theory calculation results indicated that the catalytic activities depended on orbital energy of metal complexes.

Key words: Zeolite Y, Encapsulation, Unsymmetrical Salen, Styrene, Density functional theory, Epoxidation