Rhombohedral ZnIn2S4-catalysed anodic direct electrochemical oxidative cleavage of C–O bond in α-O-4 linkages in ambient conditions,Green Chemistry

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Rhombohedral ZnIn2S4-catalysed anodic direct electrochemical oxidative cleavage of C–O bond in α-O-4 linkages in ambient conditions
Green Chemistry ( IF 9.3 ) Pub Date : 2024-02-29 , DOI: 10.1039/d4gc00338a
Qi Zhu ₁ , Bo Gong ₁ , Shuquan Huang _{1,

2} , Yangxin Jin ₁ , Shengqin Liu ₁ , Shan Shao ₁ , Yuwei Yang ₃ , Taren Cataldo ₃ , Nicholas M. Bedford ₃ , Jason Chun-Ho Lam _{1,

4}

Affiliation

The electrochemical selective oxidative transformation of lignin feedstocks into valuable oxygenated aromatics is essential to establish a sustainable biorefinery. In this study, we used a rhombohedral ZnIn₂S₄ (R-ZIS) electrocatalyst to realise the efficient anodic cleavage of C–O bonds in benzyl phenyl ether (BPE), an α-O-4 lignin model compound, to a series of industrially relevant oxygenated mono-aromatics. The reaction occurred at +2 V_Ag/AgCl, 65 °C, and atmospheric pressure. In optimised conditions, the reaction achieved over 99% conversion rate with a Faraday efficiency of 51.6% at 91.3% conversion of BPE, that is greater than most known electrocatalytic oxidative cleavage examples. The ZnIn₂S₄ electrocatalyst was deposited on a carbon cloth support, and its structural properties and surface morphology were extensively investigated. Systematic potential controlled electrolysis coupled with ¹⁸O isotopic labelling confirmed that C–O scission occurred exclusively between the benzylic carbon and phenolic oxygen. Furthermore, substrate competition studies were conducted to compare the electrocatalytic performance of the R-ZIS catalyst with that of its structural analogue, hexagonal ZnIn₂S₄, in terms of BPE and mono-aromatics conversion. The experimental results were supported by density functional theory calculations. The substrate scoping study revealed the suitability of the R-ZIS induced electrocatalytic system for a variety of substituted α-O-4/β-O-4 model dimers. Overall, this work demonstrates an efficient anodic process that can enable the atom-efficient valorisation of lignin to produce oxygenated aromatics. The proposed approach can complement the numerous existing reductive lignin cleavage methods.

中文翻译：

环境条件下菱面体 ZnIn2S4 催化阳极直接电化学氧化裂解 α-O-4 连接中的 C-O 键

将木质素原料电化学选择性氧化转化为有价值的含氧芳烃对于建立可持续的生物精炼厂至关重要。在本研究中，我们使用菱形ZnIn ₂ S ₄ (R-ZIS)电催化剂实现了α-O-4木质素模型化合物苄基苯基醚(BPE)中C-O键的高效阳极裂解，得到一系列工业相关的含氧单芳烃。反应在 +2 V _Ag/AgCl、65 °C 和大气压下发生。在优化条件下，该反应实现了超过 99% 的转化率，BPE 转化率为 91.3%，法拉第效率为 51.6%，这高于大多数已知的电催化氧化裂解实例。将ZnIn ₂ S ₄电催化剂沉积在碳布载体上，并对其结构性能和表面形貌进行了广泛研究。系统电位控制电解结合¹⁸ O 同位素标记证实 C-O 断裂仅发生在苄基碳和酚氧之间。此外，还进行了底物竞争研究，以比较 R-ZIS 催化剂与其结构类似物六方 ZnIn ₂ S ₄在 BPE 和单芳烃转化方面的电催化性能。实验结果得到了密度泛函理论计算的支持。底物范围研究揭示了 R-ZIS 诱导电催化系统对各种取代的 α-O-4/β-O-4 模型二聚体的适用性。总体而言，这项工作展示了一种有效的阳极工艺，可以实现木质素的原子效率增值，从而生产含氧芳烃。所提出的方法可以补充许多现有的还原木质素裂解方法。

更新日期：2024-02-29

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