The deposition of isolated Fe(3+) species in mesoporous silicon for oxidation of cyclohexane

The balance of activity and selectivity in liquid alkane oxidation is challenging to design supported Fe catalysts. When Fe species leach to the solvent, uncontrolled free radical chain reactions happen. Herein, we have constructed isolated Fe(3+) species by forming a strong Fe-O-Si bond for the selective oxidation of cyclohexane to cyclohexanone by H2O2. Compared to the supported FeOx clusters, the strong Fe-O-Si bond between isolated Fe(3+) species and SiO2 prevents the leaching of Fe in strong oxidation (H2O2) reaction conditions and dominates the non-free radical mechanism. The turnover frequency over the 10FeOx/SBA-15 reached 15.2 h-1, higher than the reported Fe-based catalysts. The high selectivity of cyclohexanone is maintained at different conversions. Moreover, the (SiO)xFe3+(OH)3-x-OOH active species were detected by Raman and FTIR and are generated from the oxidation of isolated Fe species. The strong Fe-O-Si bond and non-free radical mechanism by (SiO)xFe3+(OH)3-x-OOH active species induce high activity and selectivity for the oxidation of many other alkanes.