Metalloenzyme-Inspired Ce-MOF Catalyst for Oxidative Halogenation Reactions,ACS Applied Materials & Interfaces

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Metalloenzyme-Inspired Ce-MOF Catalyst for Oxidative Halogenation Reactions
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-06-27 , DOI: 10.1021/acsami.1c07496
Sergio Rojas-Buzo ₁ , Patricia Concepción ₁ , José Luis Olloqui-Sariego ₂ , Manuel Moliner ₁ , Avelino Corma ₁

Affiliation

The structure of UiO-66(Ce) is formed by CeO_2–x defective nanoclusters connected by terephthalate ligands. The initial presence of accessible Ce³⁺ sites in the as-synthesized UiO-66(Ce) has been determined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR)-CO analyses. Moreover, linear scan voltammetric measurements reveal a reversible Ce⁴⁺/Ce³⁺ interconversion within the UiO-66(Ce) material, while nanocrystalline ceria shows an irreversible voltammetric response. This suggests that terephthalic acid ligands facilitate charge transfer between subnanometric metallic nodes, explaining the higher oxidase-like activity of UiO-66(Ce) compared to nanoceria for the mild oxidation of organic dyes under aerobic conditions. Based on these results, we propose the use of Ce-based metal–organic frameworks (MOFs) as efficient catalysts for the halogenation of activated arenes, as 1,3,5-trimethoxybenzene (TMB), using oxygen as a green oxidant. Kinetic studies demonstrate that UiO-66(Ce) is at least three times more active than nanoceria under the same reaction conditions. In addition, the UiO-66(Ce) catalyst shows an excellent stability and can be reused after proper washing treatments. Finally, a general mechanism for the oxidative halogenation reaction is proposed when using Ce-MOF as a catalyst, which mimics the mechanistic pathway described for metalloenzymes. The superb control in the generation of subnanometric CeO_2–x defective clusters connected by adequate organic ligands in MOFs offers exciting opportunities in the design of Ce-based redox catalysts.

中文翻译：

金属酶激发的 Ce-MOF 催化剂用于氧化卤化反应

UiO-66(Ce)的结构是由对苯二甲酸酯配体连接的CeO _{2- x}缺陷纳米团簇形成的。已通过 X 射线光电子能谱 (XPS) 和傅里叶变换红外 (FTIR)-CO 分析确定了合成后的 UiO-66(Ce)中可访问的 Ce ³⁺位点的初始存在。此外，线性扫描伏安测量揭示了可逆的 Ce ⁴⁺ /Ce ³⁺UiO-66(Ce) 材料内的相互转化，而纳米晶二氧化铈显示出不可逆的伏安响应。这表明对苯二甲酸配体促进了亚纳米金属节点之间的电荷转移，这解释了与纳米氧化铈相比，UiO-66(Ce) 在有氧条件下对有机染料进行温和氧化具有更高的类氧化酶活性。基于这些结果，我们建议使用 Ce 基金属有机骨架（MOFs）作为活性芳烃卤化的有效催化剂，如 1,3,5-三甲氧基苯（TMB），使用氧气作为绿色氧化剂。动力学研究表明，在相同反应条件下，UiO-66(Ce) 的活性至少是纳米氧化铈的三倍。此外，UiO-66(Ce) 催化剂表现出优异的稳定性，经过适当的洗涤处理后可以重复使用。最后，当使用 Ce-MOF 作为催化剂时，提出了氧化卤化反应的一般机制，它模拟了金属酶所描述的机制途径。亚纳米级CeO 生成的极好控制_{MOF 中由足够的有机配体连接的2 – x}缺陷簇为设计 Ce 基氧化还原催化剂提供了令人兴奋的机会。

更新日期：2021-07-07

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