Iron(III), cobalt(II) and copper(II) complexes bearing 8‐quinolinol encapsulated in zeoliteY for the aerobic oxidation of styrene

A series of Fe(III), Co(II) and Cu(II) complexes of 8‐quinolinol were encapsulated into the supercages of zeoliteY and characterized by X‐ray diffraction, SEM, N2 adsorption/desorption, FT‐IR, UV–vis spectroscopy, elemental analysis, ICP‐AES and TG/DSC measurements. The encapsulation was achieved by a flexible ligand method in which the transition metal cations were first ion‐exchanged into zeolite Y and then complexed with 8‐quinolinol ligand. The metal‐exchanged zeolites, metal complexes encapsulated in zeolite–Y plus non‐encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes always showed better activity than their respective non‐encapsulated counterparts. Moreover, the encapsulated iron complex showed good recoverability without significant loss of activity and selectivity within successive runs. Heterogeneity test for this catalyst confirmed its high stability against leaching of active complex species into solution.