Zn-Nx sites on N-doped carbon for aerobic oxidative cleavage and esterification of C(CO)-C bonds

Chao Xie,Zhiwei Jiang,Zixin Wang,Buxing Han,Zehui Zhang,Longfei Lin,Liang Huang

doi:10.1038/s41467-021-25118-0

Abstract

Selective cleavage of C-C bonds is very important in organic chemistry, but remains challenging because of their inert chemical nature. Herein, we report that Zn/NC-X catalysts, in which Zn2+ coordinate with N species on microporous N-doped carbon (NC) and X denotes the pyrolysis temperature, can effectively catalyze aerobic oxidative cleavage of C(CO)-C bonds and quantitatively convert acetophenone to methyl benzoate with a yield of 99% at 100 °C. The Zn/NC-950 can be applied for a wide scope of acetophenone derivatives as well as more challenging alkyl ketones. Detail mechanistic investigations reveal that the catalytic performance of Zn/NC-950 can be attributed to the coordination between Zn2+ and N species to change the electronic state of the metal, synergetic effect of the Zn single sites with their surrounding N atoms, as well as the microporous structure with the high surface area and structural defects of the NC.

Highlights

Selective cleavage of C-C bonds is very important in organic chemistry, but remains challenging because of their inert chemical nature
Zn/N-doped carbon (NC)-950 catalyst was composed of amorphous flakes as shown in Scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM) images (Fig. 1a) and site-isolated Zn centers were dispersed over the entire flakes confirmed by HAADF-STEM and EDS mapping (Fig. 1a, b)
A loading of 0.75 wt% Zn was identified for Zn/NC-950 by inductively coupled plasma atomic emission spectroscopy (ICP-AES)

Summary

Introduction

Selective cleavage of C-C bonds is very important in organic chemistry, but remains challenging because of their inert chemical nature. Despite the great achievements that have been made, the need for substantial amounts of Cu salts and additives, and the difficulty in recovery limit their applications Heterogeneous catalyst such as Co nanoparticles was reported for catalyzing the C–C bond cleavage and esterification in C(OH)–C via C(CO)–C intermediate[25]. Zinc salts have been used as efficient catalysts for some organic transformation[26,27,28], and their catalytic performance could be adjusted by changing the coordination environment[29]. The conventional Zinc catalysts were usually used as Lewis acid for the electron-rich groups activation, such as alkyne and carbonyl groups[30] They suffered from limited substrate scopes, and intrinsic difficulty in product separation and catalyst recycling. We fabricated Zn-based heterogeneous catalysts (Zn/NC-X), in which Zn single sites [Znδ+ (0 < δ < 2)]

Methods

Results

Conclusion