Synthesis of Polyoxometalate/TiO2 Mesoporous Hybrid Materials and Their Photocatalytic Performance

A tungstophosphate derivative, (Bu4N)(3)PW11O39[O(SiOH)(2)] (TBAPW(11)Si(2)), with Si-OH groups on the surface was grafted on mesoporous TiO2 synthesized by an evaporation-induced self-assembly method. Such TBAPW(11)Si(2)/TiO2 mesoporous hybrid materials were characterized by IR, XRD, N-2 adsorption-desorption, TEM and ICP-AES techniques. It was shown that the covalent linkage between TBAPW(11)Si(2) and TiO2 formed by condensation of Si-OH on TBAPW(11)Si(2) with Ti-OH on TiO2. Enough Ti-OH groups on TiO2 surface and the calcination at a certain temperature were necessary for the condensation. Compared with TiO2 support, the hybrid samples had a little higher crystallinity of anatase, but the surface area, pore volume and pore size decreased as TBAPW(11)Si(2) loading increased. In the degradation of methyl orange, these hybrid samples exhibited higher photocatalytic activities than anatase TiO2 support, and their activities were even comparable with that of Degussa P25 with much higher crystallinity, which can be mainly attributed to a synergistic effect between polyoxometalate and TiO2.