Solvent-free oxidation of benzyl C-H to ketone with Co-Ni layered double hydroxide as the catalyst and O2 as the sole oxidant

Jiali Ren; Yan Zhou; Hui Miao; Chaoqun Wang; Shanshan Lv; Manman Song; Feng Li; Mengmeng Feng; Zheng Chen

doi:10.1039/d3dt00851g

Solvent-free oxidation of benzyl C-H to ketone with Co-Ni layered double hydroxide as the catalyst and O₂ as the sole oxidant

Dalton Trans. 2023 May 16;52(19):6398-6406. doi: 10.1039/d3dt00851g.

Authors

Jiali Ren¹, Yan Zhou², Hui Miao¹, Chaoqun Wang¹, Shanshan Lv², Manman Song², Feng Li², Mengmeng Feng², Zheng Chen²

Affiliations

¹ Anhui Provincial Key Laboratory for Degradation and Monitoring of Pollution of the Environment, School of Chemistry and Materials Engineering Fuyang Normal University, Fuyang 236037, P. R. China. huimiao@mail.ahnu.edu.cn.
² Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Materials Science, Anhui Normal University, Wuhu, 241002, China. chenzh07@mail.ahnu.edu.cn.

PMID: 37092261
DOI: 10.1039/d3dt00851g

Abstract

The aerobic oxidation of ethylbenzene is an effective way to produce acetophenone, in which solvent-free conditions and oxygen as the sole oxidant are the best choice. At present, the catalytic activity and selectivity are still at an unsatisfactory level, because efficient catalysts need to achieve both C-H bond activation and O₂ activation. In this work, the 2-methylimidazole-induced hydrolysis strategy was used to prepare a new class of CoNi-layered double hydroxide (CoNi-LDH) materials with different metal ratios. High-Resolution Transmission Electron Microscopy (HRTEM) showed that CoNi-LDH had obvious weak crystallinity and a thin lamellar structure. X-ray Photoelectron Spectroscopy (XPS) reveals the consistency between the content of the M-O component in the host layer and the proportion of Co³⁺, among which CoNi-LDH with a feed ratio (Co : Ni) of 2 : 1 (Co₂Ni-LDH) has the highest M-O content and Co³⁺ ratio. The formation of M-O is due to the H-vacancy generated by the breaking of the hydroxyl group, which can be used for the H abstraction of C-H bonds. The redox effect caused by M²⁺/M³⁺ facilitates the transfer of electrons, which promotes the activation of O₂ to the superoxide radical anion (˙O₂^-). Thereby, Co₂Ni-LDH shows the highest catalytic activity for the oxidation of ethylbenzene. Under solvent-free conditions and with oxygen as the sole oxidant, 97.8% conversion of ethylbenzene and 98.8% selectivity of acetophenone can be obtained. The excellent catalytic performance is related to the structure of CoNi-LDH, and is also the best when compared with the reported results. Various types of aromatic hydrocarbons containing benzyl C-H bonds can be effectively oxidized by CoNi-LDH to produce the corresponding ketone products.