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Understanding the Interaction of Boric Acid and CO2 with Ionic Liquids in Aqueous Medium by Multinuclear NMR Spectroscopy
journal contribution
posted on 2019-12-13, 20:12 authored by Andrei Filippov, Oleg N. Antzutkin, Faiz Ullah ShahBoric acid is known to enhance the kinetics of CO2 absorption
by some active aqueous solutions. However, the mechanism of interaction
of boric acid with CO2 in the presence of active molecules
is not yet fully understood. In this work, the interaction and dynamics
of ions in aqueous solutions of functionalized choline-based ionic
liquids [N1,1,5,2OH][Threo] and [N1,1,5,2OH][Tau]
in the presence of boric acid and CO2 was thoroughly investigated
using a multinuclear NMR approach: 13C and 11B NMR spectroscopy, 11B NMR transverse relaxation, and 1H and 11B NMR diffusometry. 13C and 11B NMR spectroscopy revealed the formation of borate-based
complexes as a result of a reaction between boric acid and the anions
of the ILs at ionic liquid/boric acid molar ratios larger than ca.
0.15. The formation of these complexes and their dynamics were further
investigated using 11B relaxation and 1H and 11B pulse-field-gradient (PFG) NMR. Plausible reaction mechanisms
of boric acid with the anions of the ILs, formation of the borate
complexes, and dissociation of these complexes facilitated by CO2 molecules are suggested.