Accurate Understanding the Catalytic Role of MnO2in the Oxidative-Coupling of 2-naphthols into 1,1′-bi-2-naphthols

It has been reported that beta-MnO2 has photocatalytic activity for the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols. Nevertheless, it is hard to exclude the possibility that the oxidative-coupling of 2-naphthols is initiated by beta-MnO2 catalysis in dark due to the insufficient investigations in the related reports. In the present work, the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols with different phases MnO2 catalysis in dark and under visible-light irradiation were systematically investigated. The results revealed that the oxidative-coupling of 2-naphthols is jointly initiated by MnO2 catalysis and O-2-oxidation, not by MnO2 photocatalysis. Among the alpha-MnO2, beta-MnO2, gamma-MnO2 and delta-MnO2 catalysis, beta-MnO(2)catalysis has the optimal performance, its selectivity for the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols is close to 100%, and its catalytic capacity could be well retained after multiple using. Our findings provide comprehensive and accurate understanding the catalytic role of MnO2 for the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols. [GRAPHICS] .

Automated summary

The catalytic role of β-MnO2 for the oxidative coupling of 2-naphthols into 1,1'-bi-2-naphthols was systematically investigated in both dark and under visible-light irradiation. Results showed that β-MnO2 catalysis had optimal performance, with high selectivity and stability even after multiple uses. This study provided a comprehensive understanding of the catalytic mechanism of MnO2 for this reaction.