Synthesis and characterization of mono substituted polyoxometalate incorporation into amorph silica and catalytic activity of these compounds in selective oxidation of aromatic amines with hydrogen peroxide

Abstract

In this study, the selective oxidation of aromatic amines using hydrogen peroxide as an green oxidant and a polyoxometalate catalyst modified with first-row transition metals in a silica matrix was performed. Initially Mono substituted Keggin type Polyoxometalates with first row transition metals (TBA)X[PW11MO39].nH2O (M= Cr, Mn, Fe, Co, Ni, Cu, Zn) were synthesised and then incorporated into a silica matrix by using sol-gel method. The synthesized compounds were characterized using techniques such as EDAX, CHNS, XRD, SEM, and TG-DTG. For selecting the best catalyst, oxidation of aniline was performed with all catalysts and polyoxometalate substituted with Fe showed best catalytic activity. After optimization reaction conditions, oxidation of different aromatic amine was performed and Fe substituted polyoxometalates showed excellent catalytic activity for selective oxidation of different amines to corresponded nitro in heterogeneous system. The studies indicated that the catalysts have good recovery capabilities and can be reused multiple times without significant loss in activity. © 2025 Semnan University.