Iron oxide nanoparticles immobilized to mesoporous NH2-SiO2 spheres by sulfonic acid functionalization as highly efficient catalysts

Abstract

A novel SiO₂ nanosphere was synthesized by the post-synthetic grafting of sulfonic acid groups on to anionic-surfactant-templated mesoporous NH₂-silica (AMAS). This one-pot post-functionalization strategy allowed more metal ions to be homogeneously anchored into the channel of the meso-SiO₂ nanosphere. After hydrothermal and calcination treatment, the in situ growth of α-Fe₂O₃ on sulfonic acid-functionalized mesoporous NH₂–SiO₂ (SA-AMAS) exhibited much higher activity in the visible-light assisted Fenton reaction at neutral pH than that for AMAS or meso-SiO₂ nanospheres. By analysis, the grafted sulfonic acid group can not only enhance the acid strength of the catalyst, but can also bring more orbital-overlapping between the active sites (Fe^II and Fe^III) and the surface peroxide species, to facilitate the decomposition of H₂O₂ to hydroxyl radical. The present results provide opportunities for developing heterogeneous catalysts with high-performance in the field of green chemistry and environmental remediation.