Bimetallic copper–gold pyrazolate complexes for photocatalytic removal and degradation of 2,4–dichlorophenoxyacetic acid

Abstract

Utilization of metal oxides and complexes in catalysis reactions has been drastically studied using transition metal ions with various ligands for improvement of catalytic activity. On the other hand, transition metal ion and oxides have been reported to give enhancement of photocatalytic activity of photocatalyst TiO2 for removal of environmental pollutants. However, there is no study on photocatalytic reaction using modification of TiO2 with bimetallic complexes. Here in, we report on first study on photocatalytic activity of bimetallic copper–gold pyrazolate complex for removal and degradation of 2,4–dichlorophenoxyacetic acid (2,4–D). The bimetallic copper–gold pyrazolate complexes were prepared by mixing gold(I) pyrazolate complex with copper(II) pyrazolate complex in dry dichloromethane for 1 hour in stoichiometric molar ratios of copper to gold; 1:0.2, 1:0.4, 1:0.6, 1:0.8, and 1:1. In order to synthesis the photocatalyst, bimetallic copper–gold pyrazolate complex was mixed with TiO2 in dichloromethane and followed by calcination at 100?C for 4 hours. Gold (I) pyrazolate complex gave 81% for percentage of 2,4– D removal using 0.4 wt% that was higher than TiO2 (80%) with the same percentage of degradation in 19%. In contrast, copper (II) pyrazolate complex with 0.4 wt% gave 98% of removal with 27% degradation of 2,4–D. Surprisingly, the resulting copper– gold with ratio of 1 to 1 gave almost the same percentage of removal but increase the degradation to 51% compared to copper(II) pyrazolate complex. The result showed that the photocatalytic activity of TiO2 can be increased by using mixture of two different metal complexes as co–catalyst.