Preparation, characterization and photocatalytic applications of amine-functionalized mesoporous silica impregnated with transition-metal-monosubstituted polyoxometalates

Amine-functionalized mesoporous silica materials impregnated with transition-metal-monosubstituted polyoxometalates, K5[M(H2O)PW11O39]-(EtO)3SiCH2CH2CH2NH2-MCM-48 (M = Co/Ni), were prepared by coordination of nickel/cobalt centers in the clusters with the amine surface groups in amine-functionalized mesoporous silica supports. The materials obtained were characterized by powder X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis-DR), infrared (IR) spectra, magic-angle spinning 31P MAS NMR, transmission electron microscopy (TEM) and nitrogen adsorption measurements, indicating that the primary Keggin structures remained intact in as-prepared composites, and the composites possessed mesoporous structures. The composites exhibited UV-photocatalytic activity to degrade dye rhodamine B (RB), and the pesticides including hexachlorobenzene (HCB) and methylparathion (MPT). Leakage of K5[M(H2O)PW11O39] from the support was hardly observed during the photocatalytic tests, attributed to strong coordination interactions between the Keggin units and the amine-functionalized silica surface. -- Graphical abstract: The K5[M(H2O)PW11O39]-(EtO)3SiCH2CH2CH2NH2-SiO2 composites were prepared by coordination of M centers in the Keggin units with the amine surface groups in amine-functionalized mesoporous silica supports, and the composites exhibited photocatalytic activity to degrade aqueous rhodamine B, hexachlorobenzene and methyl parathion