It has been reported that β-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 β-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 O2-oxidation, not by MnO2 photocatalysis. Among the α-MnO2, β-MnO2, γ-MnO2 and δ-MnO2 catalysis, β-MnO2 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. In the present work, the oxidative-coupling of 2-naphthols into 1,1′-bi-2-naphthols was proved to be jointly initiated by MnO2 catalysis and O2-oxidation, not by MnO2 photocatalysis. β-MnO2 has the optimal catalytic activity for the oxidative-coupling of 2-naphthols relative to α-MnO2, γ-MnO2 and δ-MnO2.

中文翻译：

---

准确理解 MnO2 在 2-萘酚氧化偶联成 1,1'-bi-2-萘酚中的催化作用

据报道，β-MnO2 具有光催化活性，可将 2-萘酚氧化偶联成 1,1'-bi-2-萘酚。然而，由于相关报道的研究不足，难以排除2-萘酚的氧化偶联是由β-MnO2在黑暗中催化引发的可能性。在目前的工作中，系统研究了在黑暗和可见光照射下，2-萘酚氧化偶联成具有不同相 MnO2 催化的 1,1'-bi-2-萘酚。结果表明，2-萘酚的氧化偶联是由MnO2催化和O2-氧化共同引发的，而不是由MnO2光催化引发的。在α-MnO2、β-MnO2、γ-MnO2和δ-MnO2催化中，β-MnO2催化性能最优，其对2-萘酚氧化偶联的选择性为1，1′-bi-2-萘酚接近100%，多次使用后仍能很好地保持其催化能力。我们的研究结果全面准确地理解了 MnO2 对 2-萘酚氧化偶联成 1,1'-bi-2-萘酚的催化作用。在目前的工作中，证明 2-萘酚氧化偶联成 1,1'-bi-2-萘酚是由 MnO2 催化和 O2-氧化共同引发的，而不是由 MnO2 光催化引发的。相对于α-MnO2、γ-MnO2 和δ-MnO2，β-MnO2 对2-萘酚的氧化偶联具有最佳催化活性。2-萘酚氧化偶联成1,1'-bi-2-萘酚被证明是由MnO2催化和O2-氧化共同引发的，而不是由MnO2光催化引发的。相对于α-MnO2、γ-MnO2 和δ-MnO2，β-MnO2 对2-萘酚的氧化偶联具有最佳催化活性。2-萘酚氧化偶联成1,1'-bi-2-萘酚被证明是由MnO2催化和O2-氧化共同引发的，而不是由MnO2光催化引发的。相对于α-MnO2、γ-MnO2 和δ-MnO2，β-MnO2 对2-萘酚的氧化偶联具有最佳催化活性。