Rhombohedral ZnIn₂S₄-Catalysed Anodic Direct Electrochemical Oxidative Cleavage of C-O Bond in α-O-4 Linkages in Ambient Conditions

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The electrochemical selective oxidative transformation of biomass feedstocks into valuable oxygenated fine chemicals that are essential to the bio-commodity chemical markets. In this study, we used a rhombohedral ZnIn 2 S 4 (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 (benzyl alcohol, benzaldehyde, benzoic acid, etc.). In optimised conditions, the reaction achieved over 99% conversion rate with a Faraday efficiency of 51.6% that greater than most known electrocatalytic oxidative cleavage examples. The ZnIn 2 S 4 electrocatalyst was deposited on a carbon support, and its structural properties and surface morphology were extensively investigated. Systematic chronoamperometric electrolysis coupled with 18 O isotopic labelling confirmed that C-O scission occurred exclusively between the benzylic carbon and phenolic oxygen. 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 lignin α-O-4 and 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 fine chemicals.