Selective oxidation of benzyl alcohol to benzaldehyde over Co-metalloporphyrin supported on silica nanoparticles

Heterogenation of the metalloporhyrin ligand, [tetrakis(o-chlorophenyl)porphyrinato]Co(II) was effected by immobilizing the complex onto inorganic silica support to form spherical nanoparticles of RHAC-CoPor. This insoluble mesoporous hybrid showed a high specific surface area of 114 m2 g−1 and a pore volume of 0.177 cm3 g−1. The prepared catalyst possessed a narrow pore size distribution centered at around 4.17 nm. The 13C MAS NMR showed that RHAC-CoPor had three chemical shifts at 12.60, 26.60 and 45.18 ppm consistent with the three carbon atoms of the propyl group and a series of chemical shifts in the range of δ = 108–167 ppm consistent with the presence of the metalloporphyrin complex. Elemental analysis showed the successful immobilization of metalloporphyrin complex onto functionalized RHA silica support. RHAC-CoPor appeared to be an active catalyst in the oxidation of benzyl alcohol, producing 97.1% conversion and 97.7% selectivity for benzaldehyde under an ambient temperature of 70 °C. RHAC-CoPor could be regenerated and reused several times by washing with water, followed by drying at 100 °C.

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► Tetrakis(o-chlorophenyl)porphyrinato Co(II) was immobilizing onto silica.
► The porphyrin–silica complex (RHAC-CoPor) formed spherical nanoparticles.
► RHAC-CoPor catalyzed the oxidation of benzyl alcohol to extent of 97.1%.
► A selectivity of 97.7% for benzaldehyde was achieved.