A Simple Approach to Achieve Self‐Buffering Protic Ionic Liquid‐Water Mixtures

Qi Han,Xungai Wang,Nolene Byrne

doi:10.1002/slct.201700651

Abstract

AbstractIonic liquid (IL)‐water mixtures have drawn increasing attention in a range of applications ranging from chemical synthesis and separation to bioscience and energy applications. The acid‐basic nature of ILs is often an important property to be considered when selecting and designing ILs. Herein, we evaluated this IL property by correlating the stoichiometry of a protic IL and pH of IL‐water mixtures. We then developed a simple method to achieve self‐buffering protic IL‐water mixtures by titrating buffering agents. The rule of buffering protic IL‐water mixtures was proposed to be linearly related to pIL ion concentration and correlated with ionicity. Through this approach, self‐buffering capability can be achieved in protic IL‐water mixtures without significantly changing the ion concentration.

Highlights

Ionic liquids (ILs) are salts with melting points below 100 °C
Whether the stoichiometries of acid and base affect the proton transfer of protic ILs (pILs) and pH of pIL-water mixtures were evaluated
We evaluated the proton activity and pH of TeaMs-water mixtures as a function of stoichiometry of base to acid, indicating that the stoichiometry markedly changed the pH while proton activity is not directly related to pH

Summary

Introduction

Ionic liquids (ILs) are salts with melting points below 100 °C. One of the most attractive properties of ILs is the tunability of the component ions. The ionicity refers to the degree of ionic dissociation [17], which would affect the pH of aqueous ILs. To overcome the intrinsic pH, a few studies developed IL-water mixtures with controlled pH by mixing or adding a small amount of acid or base with slightly changing ion concentration and some systems have been used for biocatalysis[11b, 18]. This two different trends of proton activity of non-stoichiometric TeaMs and the pH of pIL-water mixtures indicate that these two values are not directly related, considering that the addition of water totally changed the proton transfer of ILs[5d].

Results

Conclusion