Abstract：
Direct and selective oxidation of benzene to phenol is a long-term goal in industry. Although great efforts have been made in homogenous catalysis, it still remains a huge challenge to drive this reaction via heterogeneous catalysts under mild conditions. Herein, a single-atom Au loaded MgAl-layered double hydroxide (Au1 -MgAl-LDH) with a well-defined structure, in which the Au single atoms are located on the top of Al3+ with Au-O4 coordination as revealed by extended x-ray-absorption fine-structure (EXAFS)and density-functional theory (DFT)calculation is reported. The photocatalytic results prove the Au1 -MgAl-LDH is capable of driving benzene oxidation reaction with O2 in water, and exhibits a high selectivity of 99% for phenol. While contrast experiment shows a ≈99% selectivity for aliphatic acid with Au nanoparticle loaded MgAl-LDH (Au-NP-MgAl-LDH). Detailed characterizations confirm that the origin of the selectivity difference can be attributed to the profound adsorption behavior of substrate benzene with Au single atoms and nanoparticles. For Au1 -MgAl-LDH, single Au-C bond is formed in benzene activation and result in the production of phenol. While for Au-NP-MgAl-LDH, multiple AuC bonds are generated in benzene activation, leading to the crack of CC bond.
摘要：
将苯直接和选择性氧化为苯酚是工业中的长期目标。尽管在均相催化方面已经做出了巨大的努力，在温和条件下通过非均相催化剂驱动该反应仍然是一个巨大的挑战。在这里，具有明确结构的单原子Au负载的MgAl层状双氢氧化物（Au1-MgAl-LDH），其中Au单原子位于Al3的顶部，通过扩展的X射线吸收精细结构（EXAFS）和密度泛函理论（DFT）计算揭示了Au-O4配位。结果表明，Au1-MgAl-LDH能够驱动苯与O2在水中的氧化反应，并且对苯酚表现出99%的高选择性。而对比实验显示，对于带有Au纳米颗粒负载的MgAl-LDH（Au-NP-MgAl-LDH）的脂肪酸，选择性约为99％。详细的表征证实，选择性差异的起源可以归因于底物苯与Au单原子和纳米颗粒的深刻吸附行为。对于Au1-MgAl-LDH，在苯活化中形成单个Au-C键并导致苯酚的产生。而对于Au-NP-MgAl-LDH，在苯活化中产生多个Au-C键，导致C→C键的裂纹。
