Benign-by-design Synthesis of Covalent Triazine-Imidazolium Networks under Room Temperature Aqueous Conditions for CO2 Utilization

Abstract

In this study, we have described that the nucleophilic aromatic substitution reaction between an hydroxyl-tagged imidazolium and cyanuric chloride in a mixture of water and acetone as a reaction medium at room temperature leads to the formation of a new series of imidazolium-based covalent triazine framework (CTF). The material denoted as I-CTF-1 was identified as a family of nitrogen-rich cationic polymers. The influence of polar solvents, including pure DMSO and its aqueous solutions, as well as the presence of ionic surfactants such as CTAB or SDS, on the textural properties of the synthesized cationic CTFs has been examined. The elemental analysis indicated that the polymerization occurred meticulously, as evidenced by the strong correlation between the theoretical and experimental loading values of imidazolium and triazine groups. 13C CP-MAS NMR confirmed that both triazine and imidazolium groups are incorporated into the CTF network. The presented CTF was thermal stable till 300 ˚C. The I-CTF-1 also exhibited an interesting CO2 adsorption capacity of 2.2 mmol g-1. This catalyst displayed excellent activity toward direct coupling of carbon dioxide with various types of terminal epoxides under 1 mol% catalyst, 10 bar CO2 at 80 ˚C. It could be recycled at least 4 times without any remarkable decrease in its activity or selectivity.