Synthesis and characterization of switchable ionic compound based on DBU, CH3OH, and CO2

Switchable ionic compounds have wide applications in chemical processes. A switchable ionic compound based on 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU), CH3OH and CO2 was synthesized and characterized. DBU/CH3OH/CO2 ionic compound was prepared in the presence of excess methanol, and then the excess methanol was removed by reduced pressure distillation in CO2 atmosphere. The product yield (100%) reached the theoretical maximum for the first time. Its structure was identified by NMR, FT-IR, and XRD. The crystal product shows 8 strong peaks in XRD at 2θ values of 16.0547°, 16.4308°, 16.7651°, 18.8714°, 19.2140°, 21.9471°, 22.0780°, and 25.5661°. Its decomposition onset temperature (53 °C) was affirmed by TGA, which is lower than its melting point. And its ionic switch point was measured by conductivity.

A new synthetic method by using surplus CH3OH and a CO2 protective atmosphere, the product ratio of DBU:CH3OH:CO2 matched the theoretical ratio of 1:1:1. The pure stoichiometric ionic compound can be used as a switchable chemical in different systems to study its properties and influences on extraction, dissolution, reaction, and separation, etc.Figure optionsDownload as PowerPoint slide