Understanding the interactions between the bis(trifluoromethylsulfonyl)imide anion and absorbed CO 2 using X-ray diffraction analysis of a soft crystal surrogate

• Published in: Communications chemistry Vol. 3; no. 1; p. 143
• Main Authors: Zheng, Xin, Fukuhara, Katsuo, Hijikata, Yuh, Pirillo, Jenny, Sato, Hiroyasu, Takahashi, Kiyonori, Noro, Shin-Ichiro, Nakamura, Takayoshi
• Format: Journal Article
• Language: English
• Published: England 27.10.2020

The selective carbon dioxide (CO ) absorption properties of ionic liquids (ILs) are highly pertinent to the development of methods to capture CO . Although it has been reported that fluorinated components give ILs enhanced CO solubilities, it has been challenging to gain a deep understanding of the interactions occurring between ILs and CO . In this investigation, we have utilized the soft crystalline material [Cu(NTf ) (bpp) ] (NTf  = bis(trifluoromethylsulfonyl)imide, bpp = 1,3-bis-(4-pyridyl)propane) as a surrogate for single-crystal X-ray diffraction analysis to visualize interactions occurring between CO and NTf , the fluorinated IL component that is responsible for high CO solubility. Analysis of the structure of a CO -loaded crystal reveals that CO interacts with both fluorine and oxygen atoms of NTf anions in a trans rather than cis conformation about the S-N bond. Theoretical analysis of the structure of the CO -loaded crystal indicates that dispersion and electrostatic interactions exist between CO and the framework. The overall results provide important insight into understanding and improving the CO absorption properties of ILs.