Facile fabrication of Cu single atoms through nano-constrained environment

In recent years, single-atom catalysts (SACs) have become a hotspot of research in catalysis due to their specific coordination structure and the maximization of metal utilization. Nonetheless, owing to the quality of easy metal aggregation in catalysts, the preparation of SACs can be complicated. To that end, in a new study published in Green Chemical Engineering, a research team led by Prof Lin-Bing Sun at Nanjing Tech University reported the easy preparation of copper SAC.

“Specifically, the copper SAC was prepared in mesoporous silica KIT-6 by grinding and calcination using the nano-constrained environment between the templating agent and the silica wall,” shares Sun. “The resulting product displays excellent catalytic performance in CO₂ cycloaddition reactions.”

Typically, the mesoporous silica KIT-6 prepared with a template known as template-occupied KIT-6 (TOK) undergoes calcination. This process eliminates the template, resulting in template-free KIT-6 (TFK), which is then utilized for functionalization. “In fact, TOK contains nano-constrained environment between the silica wall and template, which may prevent metal agglomeration and potentially result in the production of single atoms,” says Sun.

In this study, the researchers exploited the nano-constrained environment in TOK. The precursor Cu(NO₃)₂ can be effectively introduced into the nano-constrained environment through grinding, and the mixture is subsequently calcined to form Cu SAC, referred to as CuTOK. The experimental data and results of density functional theory show that the Cu exists as Cu-O-Si.

“CuTOK was used in the CO₂ cycloaddition of epichlorohydrin with a yield of 91.7%, which was significantly higher than which of CuTFK (58.3%),” explains Sun. “Additionally, CuTOK shows a turnover frequency (TOF) of 127.3 h^-1, which is considerably higher than the TOF values of other Cu-containing catalysts, which range from 5.5 to 49.4 h^-1.”

The researchers noted that the facile strategy can be extended to prepare single-atom catalysts of other metals, providing a convenient and novel idea for the preparation of SACs.

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Contact the author: Lin-Bing Sun, State Key Laboratory of Materials-Oriented Chemical Engineering, Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China, lbsun@njtech.edu.cn

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