Iron(III) porphyrin supported on metahalloysite: an efficient and reusable catalyst for oxidation reactions

The raw clay minerals kaolinite and halloysite were calcined at controlled temperature and time, to obtain metakaolinite and metahalloysite, respectively. The resulting materials were used as supports for the anionic iron(III) porphyrin [Fe(TDFSPP)] (FePor) and found that only metahalloysite is adequate for FePor immobilization, although the FePor loading on this solid is low. XRPD, FTIR and solid UV-Vis spectroscopies, and textural analysis confirmed metakaolinite and metahalloysite formation and FePor immobilization on metahalloysite. The catalytic activity of the metahalloysite-supported FePor (FeMhallo) was evaluated in heterogeneous oxidation reactions using iodosylbenzene as oxidant and cyclooctene, cyclohexane, or n-heptane as substrate, obtaining expressive product yields for all the substrates. At the end of the oxidation, the catalyst was recovered from the reaction medium and used in a further reaction, which also afforded appreciable results. In competitive catalytic reactions using cyclohexane and n-heptane as substrates, FeMhallo is not significantly selective for any of the substrates.