Yuanqing He, Xu Zeng, Zhuoran Lu, Shiheng Mo, Qizheng An, Qinghua Liu, Yulu Yang, Wu Lan, Shuangyin Wang, Yuqin Zou
{"title":"Aqueous Electrocatalytic Hydrogenation Depolymerization of Lignin β-O-4 Linkage via Selective C<sub>aryl</sub>-O(C) Bond Cleavage: The Regulation of Adsorption.","authors":"Yuanqing He, Xu Zeng, Zhuoran Lu, Shiheng Mo, Qizheng An, Qinghua Liu, Yulu Yang, Wu Lan, Shuangyin Wang, Yuqin Zou","doi":"10.1021/jacs.4c12220","DOIUrl":null,"url":null,"abstract":"<p><p>The cleavage of the benzene-oxygen (C<sub>aryl</sub>-O(C)) bond of the lignin β-O-4 linkage is expected to relieve condensation of the degradation product and improve the product value. Nevertheless, the electrochemical breaking of the C<sub>aryl</sub>-O(C) bond has not been achieved yet due to the high dissociation energy (∼409 kJ mol<sup>-1</sup>) and the easy over-reduction of aromatic compounds. Here, we report an aqueous electrochemical reduction strategy for breaking C<sub>aryl</sub>-O(C) bonds via the regulation of molecular adsorption. The density functional theory (DFT) calculations and quartz crystal microbalance (QCM) measurements reveal that the residual Cu(I) in the CuO electrocatalyst enhances the adsorption of the 2-phenoxy-1-phenylethyl alcohol (PPE) by the C<sub>aryl</sub>-O(C) bond and lowers the energy barrier of the protons attacking the oxygen atom in the β-O-4 linkage. Thus, compared to the Cu electrocatalyst (with a hydroquinone yield of 47.4% and a benzyl alcohol yield of 24.8%), the CuO nanorod exhibits a much higher yield of hydroquinone (95.3%) and benzyl alcohol (88.6%) at a potential of -0.4 V vs reversible hydrogen electrode (RHE) in an undivided cell. Moreover, the reaction pathway and the cleavage of the C<sub>aryl</sub>-O(C) bond are identified through a combination of in situ synchrotron-radiation Fourier transformed infrared spectroscopy (SR-FTIR) and DFT calculations. This effective method is utilized for poplar lignin electrolysis, yielding 10.9 wt % of guaiacylglycerol, with an outstanding selectivity of >63.0%. This work provides an efficient and mild method of cleavage of C<sub>aryl</sub>-O(C) bonds in lignin valorization.</p>","PeriodicalId":49,"journal":{"name":"Journal of the American Chemical Society","volume":null,"pages":null},"PeriodicalIF":14.4000,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of the American Chemical Society","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/jacs.4c12220","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The cleavage of the benzene-oxygen (Caryl-O(C)) bond of the lignin β-O-4 linkage is expected to relieve condensation of the degradation product and improve the product value. Nevertheless, the electrochemical breaking of the Caryl-O(C) bond has not been achieved yet due to the high dissociation energy (∼409 kJ mol-1) and the easy over-reduction of aromatic compounds. Here, we report an aqueous electrochemical reduction strategy for breaking Caryl-O(C) bonds via the regulation of molecular adsorption. The density functional theory (DFT) calculations and quartz crystal microbalance (QCM) measurements reveal that the residual Cu(I) in the CuO electrocatalyst enhances the adsorption of the 2-phenoxy-1-phenylethyl alcohol (PPE) by the Caryl-O(C) bond and lowers the energy barrier of the protons attacking the oxygen atom in the β-O-4 linkage. Thus, compared to the Cu electrocatalyst (with a hydroquinone yield of 47.4% and a benzyl alcohol yield of 24.8%), the CuO nanorod exhibits a much higher yield of hydroquinone (95.3%) and benzyl alcohol (88.6%) at a potential of -0.4 V vs reversible hydrogen electrode (RHE) in an undivided cell. Moreover, the reaction pathway and the cleavage of the Caryl-O(C) bond are identified through a combination of in situ synchrotron-radiation Fourier transformed infrared spectroscopy (SR-FTIR) and DFT calculations. This effective method is utilized for poplar lignin electrolysis, yielding 10.9 wt % of guaiacylglycerol, with an outstanding selectivity of >63.0%. This work provides an efficient and mild method of cleavage of Caryl-O(C) bonds in lignin valorization.
期刊介绍:
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