Zeolite Y encapsulated Cu (II) and Zn (II)-imidazole-salen catalysts for benzyl alcohol oxidation

To mimic biological enzyme in catalysis, metal-imidazole-salen complexes were proposed (via DFT calculation) and synthesized in situ within the cavities of Y zeolite. Among the synthesized zeozymes, the Cu-salenIIY exhibited a prominent catalytic efficiency for the selective oxidation of benzyl alcohol. Specifically, the activity and selectivity of the encapsulated catalyst were comparable to those of the free Cu-salenII complex in solution. Furthermore, the high activity and selectivity were preserved during the repeated cycles. The similarity in the initial activity implies that the Cu-salenII complex just resides in the cavity of the zeolite Y, and its intrinsic properties responsible for the catalytic activity keep intact after encapsulation. The confinement of zeolite nanocavities effectively inhibited the dimerization or aggregation of the Cu-salenII complex and prevented the active species from escaping into reaction solution, thus resulting in a remarkably improved in the catalytic reusability and durability.