Recently, the School of Chemical Engineering and Materials at Tianjin University of Science and Technology (TUST) has made significant progress in developing a continuous-flow electrocatalytic oxidation process for the selective oxidation of toluene C(sp³)‒H bonds to produce high-value-added oxygenated chemicals, based on electrocatalytic membranes. The related research findings, entitled "A Green and Efficient Electrocatalytic Route for the Highly-Selective Oxidation of C–H Bonds in Aromatics over 1D Co₃O₄-Based Nanoarrays," have been published in the prestigious international journal Angewandte Chemie International Edition. TUST is listed as the first author and corresponding author institution. Yin Zhaohui, a PhD candidate, and Luo Lan, a young faculty member, both from the School of Chemical Engineering and Materials, are co-first authors of the paper. Professor Yin Zhen is the corresponding author. Scholars from Peking University, Tiangong University, and the German Electron Synchrotron Center (DESY) also participated in this work.

The selective oxidation of C(sp³)‒H bonds in aromatic hydrocarbons (such as toluene, p-xylene) to produce alcohols, aldehydes, and carboxylic acids is an industrially important catalytic oxidation process. Addressing issues in traditional thermal catalytic routes like high energy consumption, numerous by-products, and CO₂ emissions, the team designed and developed highly efficient electrocatalytic membrane electrodes (ECMEs) using a microfiltration membrane as the substrate. They successfully achieved the highly selective and sustainable flow synthesis of various high-value-added oxygenated products (benzyl alcohol, benzaldehyde, and benzyl acetate) from toluene via electrocatalytic selective oxidation, providing new insights for the green synthesis of organic compounds through electrocatalysis.

This research utilized a porous microfiltration metal membrane (titanium membrane) as the substrate and employed an in-situ growth strategy to construct one-dimensional Co₃O₄ nanoneedle arrays (Co₃O₄ NNs/Ti) and Co₃O₄@MnO₂ core-shell structured array catalysts (Co₃O₄@MnO₂/Ti). These served as the anode to build an electrocatalytic membrane reactor (ECMR), developing a green and efficient continuous-flow electrocatalytic oxidation process for the selective oxidation of toluene. The results show that on the Co₃O₄ NNs/Ti membrane electrode, toluene conversion reached 47.6%, with benzaldehyde as the main oxidation product and a maximum selectivity of 90%. In contrast, the primary product on the Co₃O₄@MnO₂/Ti membrane electrode was benzyl alcohol, with a selectivity as high as 90.1% and a toluene conversion of 32.1%. Notably, at high current density (>1.5 mA cm⁻²), the toluene oxidation conversion reached 58.5%, with benzyl acetate selectivity reaching up to 92%. This study demonstrates that modulating the surface/interface of the catalyst can successfully alter the oxidation products and selectivity from toluene.

The study also employed Density Functional Theory (DFT) calculations to investigate the influence of changes in the surface/interface electronic structure of the catalyst on the oxidation reaction pathway. The results indicate that modifying Co₃O₄ with MnO₂ can modulate the electronic structure of the core-shell catalyst, thereby regulating the adsorption behavior of intermediate species and the reaction pathway. This work demonstrates a sustainable, continuous-flow electrocatalytic reaction and electrochemical synthesis process for the precise control of value-added product selectivity in the electrochemical oxidation of aromatics, providing important guidance for the selective oxidation of inert C-H bonds and research on electrocatalytic membranes. This research was supported by the National Natural Science Foundation of China and the Tianjin Natural Science Foundation for Distinguished Young Scholars, among other projects.

The first author, Yin Zhaohui, a PhD candidate enrolled in 2021 at the School of Chemical Engineering and Materials, has published over ten papers in journals such as Angew. Chem. Int. Ed, Sci. China Mater., and Ind. Eng. Chem. Res., has presided over and completed one Tianjin Graduate Scientific Research Innovation Project, and has received honors including the National PhD Scholarship, the Tianjin Wang Kechang Scholarship, and the Tianjin Outstanding Student award.

In recent years, aligned with the national "Dual Carbon" strategy and focusing on distinctive salt chemical research, the School of Chemical Engineering and Materials has actively connected with the needs of the Beijing-Tianjin-Hebei coordinated development and Tianjin's "1+3+4" modern industrial system, accelerating the layout in chemical new materials, new energy, and green low-carbon technologies. The School actively promotes the transformation of scientific research achievements to serve the regional economy and social development of the Beijing-Tianjin-Hebei area, undertaking more than 100 enterprise-commissioned projects annually to assist the green, low-carbon transformation, and upgrading of chemical and new materials-related enterprises and industries. It actively promotes cooperative research with renowned domestic and international institutions, publishing over 100 high-level papers annually in related fields of chemical engineering and materials. Simultaneously, the School places high importance on postgraduate cultivation, addressing major national needs through genuine research projects, exploring ways to cultivate and enhance postgraduate innovation and practical ability through scientific research projects, promoting the reform of postgraduate teaching and training models, focusing on high-quality development, striving to advance the tasks of the "Pioneer Plan," and contributing to the university's high-quality, connotative development.

Link to the article:
https://onlinelibrary.wiley.com/doi/10.1002/anie.202415044