Luminescent group 11 3,5-dimethyl pyrazolate complexes/titanium oxide composites for photocatalytic removal and degradation of 2,4-dichlorophenoxyacetic acid

Abstract

We report the successful preparation of new luminescent group 11 pyrazolate complex/titanium oxide composites for the significant improvement of photocatalytic activity in the removal and degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D). Photocatalyst composites were successfully prepared using an impregnation method of all complexes (M(I or II)) in weight ratios of 0.1-1.0 wt% to TiO2. In contrast to anatase TiO2 with 49% for removal and 10% for degradation, the composites Au(I)/TiO2 and Ag(I)/TiO2 with 0.4 wt% gave the highest removal and degradation in 85% and 36% in 1 h. Interestingly, the composite Cu(I)/TiO2 with 0.4 wt% gave even better removal in 99% and almost the same percentage of degradation. By using the same ligand for the complexation, the photocatalyst composite Cu(II)/TiO2 with the same composition was found to show enhancement in the degradation from 36% to 48% with similar percentage of the removal. These results showed that group 11 pyrazolate complexes in TiO2 composites could able to significantly improve the photocatalytic activity due to the reduction of electron-hole recombination of TiO2. Moreover, Cu(I) pyrazolate with longer metal-metal distance (emission peak at 590 nm) for electron transfer from the conduction band is responsible for such performance in the removal. Indeed, dinuclear Cu(II) pyrazolate complex with less rigid structure has more longer metal-metal distance (566 nm) to give such better performance in the degradation. This work demonstrated that modification of TiO2 with group 11 pyrazolate complexes at the molecular level as photocatalyst composites is a new approach to enhance photocatalytic activity.