Constructing a fragmentary g-C 3 N 4 framework with rich nitrogen defects as a highly efficient metal-free catalyst for acetylene hydrochlorination

• Published in: Catalysis science & technology 2019-07, Vol.9 (14), p.3753-3762
• Main Authors: Qiao, Xianliang, Zhou, Zhiqiang, Liu, Xinyu, Zhao, Chaoyue, Guan, Qingxin, Li, Wei
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/C9CY00927B

Graphitic carbon nitride (denoted as “g-C 3 N 4 ”), as a graphite-like CN material, is widely used in catalysis. In this paper, a fragmentary g-C 3 N 4 framework with a porous structure and rich nitrogen defects was synthesized for acetylene hydrochlorination, using melamine formaldehyde (MF) resin as an oxygen-containing precursor. The fragmentary g-C 3 N 4 shows a highly efficient activity with acetylene conversion reaching 94.5%, which is 30 times higher than that of pure g-C 3 N 4 prepared by direct pyrolysis of melamine. Both experimental and characterization studies by XRD, XPS and TG-MS reveal that the high activity of the catalyst is mainly derived from the porous structure and rich nitrogen defects, which are attributed to the etching of the g-C 3 N 4 framework by oxygen species in the MF resin. Moreover, density functional theory (DFT) calculations demonstrated that the nitrogen defects in the g-C 3 N 4 framework greatly improved the adsorption of HCl and acetylene, and at the same time significantly reduced the energy barrier from 62.0 to 38.1 kcal mol −1 at the rate-determining step.