Immobilized metalloporphyrins in mesoporous MCM-48 as efficient and selective heterogeneous catalysts for oxidation of cyclohexene

Three metalloporphyrins, Mn(III)TClPPCl, Fe(III)TClPPCl, and Co(II)TClPP (TClPP = 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin), were synthesized and immobilized in MCM-48 channels. The designed heterogeneous catalysts were characterized by XRD, ICP, UV-Vis, FT-IR, N-2 adsorption-desorption, and scanning electron microscopy. These investigations showed that successful encapsulation occurred and the framework of mesoporous MCM-48 was retained without any change after incorporation of the metalloporphyrins. The effect of the support on the resistance to pore blocking was studied by comparing MCM-48 with MCM-41. The catalytic activities of the newly synthesized catalysts were examined in the oxidation of cyclohexene with t-butyl hydroperoxide as oxidant. All results confirmed that the supported catalysts presented interesting advantages such as high selectivity to the allylic products and more resistance to pore blocking. The heterogeneous catalysts were reused for several times without significant loss of their catalytic activity.