Adsorption of an iron(III)porphyrin onto a 2:1 Zn/Al-CO3 layered double hydroxide and its use as an oxidation catalyst with different counter ions: An experimental and DFT study

Abstract

DFT calculations were employed in order to gain insight about the mechanism of the oxidation reaction catalyzed by anionic iron(III) porphyrin ([Fe(TSPP)Cl]4−) with different counter ions (H+ and Na+) immobilized onto Zn4Al2(OH)12(CO3).4H2O layered double hydroxide. The immobilization of these porphyrinates was modelled by the construction of a LDH slab and the CI-NEB method was used to obtain the reaction path of the H2O2 cleavage and the subsequent formation of the oxoiron species. The computational simulations predicted that the counter ion affects the energy barriers of the oxoiron species formation. On the experimental side, the solid catalysts were synthesized and their catalytic performances were tested for the oxidation reaction of cyclohexane. The experiments showed that the immobilization process of the catalysts led to a selectivity of alcohol formation compared to the catalysis in homogeneous media. Furthermore, the reaction yield of the iron(III) porphyrin with H+ was higher, confirming that the consideration of the counter ion for the catalyst is important for oxidation reactions.