Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

• Published in: Nature communications Vol. 14; no. 1; p. 4509
• Main Authors: Yan, Hao, Liu, Bowen, Zhou, Xin, Meng, Fanyu, Zhao, Mingyue, Pan, Yue, Li, Jie, Wu, Yining, Zhao, Hui, Liu, Yibin, Chen, Xiaobo, Li, Lina, Feng, Xiang, Chen, De, Shan, Honghong, Yang, Chaohe, Yan, Ning
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26.07.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/638/224/685; 639/638/77/887; 639/638/898; Acids; Catalysts; Catalytic activity; Coordination numbers; Formic acid; Glycerol; Humanities and Social Sciences; Lewis acid; Lewis base; Manganese dioxide; Metal oxides; multidisciplinary; Noble metals; Oxidation; Oxygen; Polyols; Science; Science (multidisciplinary); Substrates; Sugar
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-40306-w

Oxidation of renewable polyol/sugar into formic acid using molecular O 2 over heterogeneous catalysts is still challenging due to the insufficient activation of both O 2 and organic substrates on coordination-saturated metal oxides. In this study, we develop a defective MnO 2 catalyst through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. Compared to common MnO 2 , the tri-coordinated Mn in the defective MnO 2 catalyst displays the electronic reconstruction of surface oxygen charge state and rich surface oxygen vacancies. These oxygen vacancies create more Mn δ+ Lewis acid site together with nearby oxygen as Lewis base sites. This combined structure behaves much like Frustrated Lewis pairs, serving to facilitate the activation of O 2 , as well as C–C and C–H bonds. As a result, the defective MnO 2 catalyst shows high catalytic activity (turnover frequency: 113.5 h −1 ) and formic acid yield (>80%) comparable to noble metal catalysts for glycerol oxidation. The catalytic system is further extended to the oxidation of other polyols/sugars to formic acid with excellent catalytic performance. This work develops defective MnO2 catalysts with Frustrated Lewis Pairs through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid.