| Summary: | In search of robust catalysts for redox transformations such as the hydrogen evolution reaction (HER) or CO<sub>2</sub> to CO reduction, we stepped on the previously reported <i>meso</i>-tetrakis(3,4,5-trimethoxyphenyl)porphyrinato cobalt(II) complex [Co(TTMPP)]. We prepared [Co(TTMPP)] in good yields and characterized it by IR, UV-vis absorption, photoluminescence spectroscopy, and cyclic voltammetry (CV). The [Co(TTMPP)] was used as a homogeneous catalyst for the electrochemical formation of H<sub>2</sub> (HER) in DMF (<i>N,N</i>’-dimethylformamide)/TFA (trifluoroacetic acid) and DMF/EtN<sub>3</sub>BF<sub>4</sub> solutions, with high faradic efficiencies (<i>FE</i>). Additionally, the reduction of CO<sub>2</sub> to CO in DMF under a CO<sub>2</sub> atmosphere was catalyzed in DMF/TFE (TFE = 2,2,2-trifluoroethanol) and DMF/PhOH with high <i>FE</i> and only traces of H<sub>2</sub> as a by-product. Turnover frequencies of 15.80 or 9.33 s<sup>−1</sup>, respectively were determined from CV experiments or controlled potential electrolysis in the presence of 1eq. TFE. They were lower with PhOH as proton source with 13.85 or 8.31 s<sup>−1</sup>, respectively. Further, [Co(TTMPP)] as a solid catalyst (suspension) allowed the photodecomposition of the organic dyes methylene blue (MB) and rhodamine B (RhB) using H<sub>2</sub>O<sub>2</sub> under visible light irradiation. The photocatalyst was photostable over five cycles. A photocatalytic mechanism was proposed based on trapping experiments of reactive oxygen species.
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