Efficient and stable photocatalysts for selective oxidative coupling of amines to imines are crucial to the conversion of sustainable solar energy to value-added chemical energy. In this work, UiO-66-NH₂@Au@COF core–shell nanocomposites with intercalated Au nanoparticles between the UiO-66-NH₂ core and the covalent-organic framework (COF) shell have been demonstrated to exhibit enhanced activity and stability for visible-light-driven aerobic selective oxidation of amines to imines. With optimized Au and two-dimensional π-conjugated COF content, the obtained UiO-66-NH₂@Au_0.5@COF1 photocatalyst exhibited the highest conversion of benzylamine with an imine yield of 66.9% for at least five cycles. It is revealed that the introduction of appropriate Au and COF could not only broaden the visible-light absorption band but also promote the separation of photoinduced charge carriers and enhance the photocatalytic performance. Furthermore, a rational mechanism was explored to elucidate the process of photocatalytic reaction. The intercalated Au nanoparticles with the localized surface plasmon resonance (LSPR) effect act as generators of hot electrons and also transfer channels for the photo-generated electrons from the COF shell to the UiO-66-NH₂ core. Importantly, the MOF@metal@COF photocatalysts might provide a promising strategy to construct photocatalysts with desirable activity and stability under visible-light illumination.

中文翻译：

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可见光诱导的胺在 UiO-66-NH2@Au@COF 核壳光催化剂上选择性氧化成亚胺

用于胺与亚胺选择性氧化偶联的高效且稳定的光催化剂对于将可持续太阳能转化为具有附加值的化学能至关重要。在这项工作中，UiO-66-NH ₂ @Au@COF 核壳纳米复合材料在 UiO-66-NH ₂核和共价有机骨架 (COF) 壳之间插入了 Au 纳米颗粒，已被证明具有增强的活性和稳定性用于在可见光驱动下将胺选择性氧化为亚胺。优化Au和二维π共轭COF含量，得到UiO-66-NH ₂ @Au _0.5@COF1 光催化剂在至少五个循环中表现出最高的苄胺转化率，亚胺产率为 66.9%。结果表明，适当的Au和COF的引入不仅可以拓宽可见光吸收带，还可以促进光生电荷载流子的分离，提高光催化性能。此外，探索了一个合理的机制来阐明光催化反应的过程。具有局域表面等离子体共振 (LSPR) 效应的嵌入 Au 纳米粒子充当热电子的发生器，并将光生电子从 COF 壳转移到 UiO-66-NH ₂核。重要的是，MOF@metal@COF 光催化剂可能为构建在可见光照射下具有理想活性和稳定性的光催化剂提供了一种有前景的策略。