Immobilization of phosphomolybdic acid on the surface of mesoporous silica functionalized with alkylammonium groups

Silica containing protonated 3-aminopropyl groups has been synthesized by a template method using Pluronic 123 as a surfactant in an acidic medium at a hydrochloric acid concentration of 1.72 M. The X-ray diffraction data have indicated that the obtained sample has a highly ordered hexagonal structure, which agrees with the large specific surface area and sorption pore volume ( S sp = 880 m 2 /g, V s = 1.28 cm 3 /g) typical of SBA-15 materials. However, transmission electron microscopy data show that this material contains two phases, with one of them being similar to SBA-15 mesoporous silica and the other belonging to socalled “honeycomb foams.” An ion-exchange reaction has been employed to immobilize phosphomolybdic acid H 3 [P(Mo 3 O 10 ) 4 ] on the pore surface, and the fact of immobilization has been confirmed by IR and TGA data. This functionalization significantly reduces the S sp and V s values of the sample but has no effect on isotherm pattern, thereby attesting to retaining the silica structure after the modification.