Zeolite Incorporated Copper-Schiff Base Complex: Synthesis, Characterization and Heterogeneous Catalytic Oxidation

A zeolite immobilized hybrid catalyst Cu(MeO-salpn)-NaY has been synthesized by incorporating Cu(II) Schiff base [where MeO-salpnH2 is N,N′-(propane-1,3)-bis-(3-methoxysalicylaldiimine)] complex in the porous matrix of zeolite NaY. The prepared hybrid material has been characterized by infrared, UV-visible spectra, powder X-ray diffraction (XRD) and thermogravimetric (TG-DTA) analyses. The X-ray powder diffraction analysis showed that the crystalline integrity of the pristine NaY zeolite remained intact upon immobilization of the complex. Spectroscopic study indicates that CuN2O2 basal plane of neat complex undergoes distortion upon immobilization of the complex in zeolite cavity. The hybrid catalyst was employed in the oxidation reactions of phenol and 1-naphthol and found to be catalytically active with impressive selectivity. At the same time, free complex [Cu(MeO-salpn)(H2O)] and hybrid material Cu-NaY were prepared and applied for the same reactions, but the catalytic activity of these species were found to be very poor. This study shows that there occurs a distortion of the coordination environment around copper(II) upon immobilization which is a major reason behind the different catalytic activity of these copper-Schiff base systems.