Highly Selective Activation of C-H Bond and Inhibition of C-C Bond Cleavage by Tuning Strong Oxidative Pd Sites

Meng Guo; Peijie Ma; Lu Wei; Jiayi Wang; Zhiwei Wang; Kun Zheng; Daojian Cheng; Yuxi Liu; Hongxing Dai; Guangsheng Guo; Erhong Duan; Jiguang Deng

doi:10.1021/jacs.3c00747

Highly Selective Activation of C-H Bond and Inhibition of C-C Bond Cleavage by Tuning Strong Oxidative Pd Sites

J Am Chem Soc. 2023 May 24;145(20):11110-11120. doi: 10.1021/jacs.3c00747. Epub 2023 May 16.

Authors

Meng Guo¹, Peijie Ma², Lu Wei¹, Jiayi Wang³, Zhiwei Wang¹, Kun Zheng², Daojian Cheng³, Yuxi Liu¹, Hongxing Dai¹, Guangsheng Guo¹, Erhong Duan⁴, Jiguang Deng¹

Affiliations

¹ Key Laboratory of Beijing on Regional Air Pollution Control, Beijing Key Laboratory for Green Catalysis and Separation, Center of Excellence for Environmental Safety and Biological Effects, Beijing University of Technology, Beijing 100124, China.
² Beijing Key Laboratory of Microstructure and Properties of Solids, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China.
³ State Key Laboratory of Organic-Inorganic Composites, Beijing Key Laboratory of Energy Environmental Catalysis, Beijing University of Chemical Technology, Beijing 100029, China.
⁴ School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, China.

PMID: 37191364
DOI: 10.1021/jacs.3c00747

Abstract

Improving the product selectivity meanwhile restraining deep oxidation still remains a great challenge over the supported Pd-based catalysts. Herein, we demonstrate a universal strategy where the surface strong oxidative Pd sites are partially covered by the transition metal (e. g., Cu, Co, Ni, and Mn) oxide through thermal treatment of alloys. It could effectively inhibit the deep oxidation of isopropanol and achieve the ultrahigh selectivity (>98%) to the target product acetone in a wide temperature range of 50-200 °C, even at 150-200 °C with almost 100% isopropanol conversion over PdCu_1.2/Al₂O₃, while an obvious decline in acetone selectivity is observed from 150 °C over Pd/Al₂O₃. Furthermore, it greatly improves the low-temperature catalytic activity (acetone formation rate at 110 °C over PdCu_1.2/Al₂O₃, 34.1 times higher than that over Pd/Al₂O₃). The decrease of surface Pd site exposure weakens the cleavage for the C-C bond, while the introduction of proper CuO shifts the d-band center (ε_d) of Pd upward and strengthens the adsorption and activation of reactants, providing more reactive oxygen species, especially the key super oxygen species (O₂^-) for selective oxidation, and significantly reducing the barrier of O-H and β-C-H bond scission. The molecular-level understanding of the C-H and C-C bond scission mechanism will guide the regulation of strong oxidative noble metal sites with relatively inert metal oxide for the other selective catalytic oxidation reactions.