Efficient and Selective Photocatalytic Cyclohexane Oxidation on a Layered Titanate Modified with Iron Oxide under Sunlight and CO2 Atmosphere

Layered titanates modified with molecular level iron oxide were synthesized by a reaction between K0.7Ti1.73Li0.27O4 and Fe(III) acetylacetonate complex using the dodecylammonium-exchanged layered titanate as intermediate. The iron oxide-modified layered titanates were used as catalysts for selective oxidation of cyclohexane with molecular oxygen under sunlight irradiation. The catalysts produced cyclohexanone and cyclohexanol with high selectivity up to 100% and showed cyclohexane conversion comparable to that obtained over a commercially available TiO2 (P25), depending on the amount of the attached iron oxide. The results were explained by the molecular recognitive cyclohexane adsorption ability of the catalysts, that is, the inhibition of the successive oxidation of the formed products. The cyclohexane conversion over the iron oxide-modified layered titanates was substantially improved with 100% selectivity maintained by conducting the reaction under a CO2 atmosphere.