Potocatalytic oxidative degradation of organic pollutant with molecular oxygen activated by a novel biomimetic catalyst ZnPz(dtn-COOH)4

Abstract

Zinc porphyrins and its analogs showing many excellent properties such as good potosensitivity, non-toxicity, high stability and facile preparation attract more and more attention of scientists. Here, a novel zinc porphyrazine, namely zinc(II) tetracarboxyl- tetra(1,4-dithiin) porphyrazine [abbreviated as ZnPz(dtn-COOH)4] was successfully synthesized and its potocatalytic activity was studied. The ZnPz(dtn-COOH)4 supported on an Amberlite CG-400 resin was used as a biomimetic catalyst for the activation of molecular oxygen under visible light to degrade a probe dye compound Rhodamine B (RhB) in aqueous solution. Interestingly, the mechanism for the oxidative degradation of RhB involves both 1O2 and HO (Type II and Type I mechanisms, respectively). More hydroxyl radicals were produced at pH 3, which was responded for the highest degradation ratio. The catalyst can be reused several times without losing its catalytic activity, with an average RhB degradation ratio around 80% for 12h. The most probable mechanism of RhB degradation in this study was that N,N-diehyl-N-ethyl-rhodamine was the main intermediate, which was then cleaved to small molecule by reactive oxidizing species. This study demonstrated a promising approach for the activation of molecular oxygen by the newly developed biomimetic catalyst, in which the central metal to be unchangeable valence, for environmental remediation and oxidation catalysis.