Metal complexes are extensively explored as catalysts for oxidation reactions; molecular-based mechanisms are usually proposed for such reactions. However, the roles of the decomposition products of these materials in the catalytic process have yet to be considered for these reactions. Herein, the cyclohexene oxidation in the presence of manganese(III) 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine chloride tetrakis(methochloride) (1) in a heterogeneous system via loading the complex on an SBA-15 substrate is performed as a study case. A molecular-based mechanism is usually suggested for such a metal complex. Herein,1was selected and investigated under the oxidation reaction by iodosylbenzene or (diacetoxyiodo)benzene (PhI(OAc)2). In addition to1, at least one of the decomposition products of1formed during the oxidation reaction could be considered a candidate to catalyze the reaction. First-principles calculations show that Mn dissolution is energetically feasible in the presence of iodosylbenzene and trace amounts of water.