In recent years, the designer nature of ionic liquids (ILs) has driven their exploration and exploitation in countless fields among the physical and chemical sciences. A fair measure of the tremendous attention placed on these fluids has been attributed to their inherent designer nature. And yet, there are relatively few examples of reviews that emphasize this vital aspect in an exhaustive or meaningful way. In this critical review, we systematically survey the physicochemical properties of the collective library of ether- and alcohol-functionalized ILs, highlighting the impact of ionic structure on features such as viscosity, phase behavior/transitions, density, thermostability, electrochemical properties, and polarity (e.g. hydrophilicity, hydrogen bonding capability). In the latter portions of this review, we emphasize the attractive applications of these functionalized ILs across a range of disciplines, including their use as electrolytes or functional fluids for electrochemistry, extractions, biphasic systems, gas separations, carbon capture, carbohydrate dissolution (particularly, the (ligno)celluloses), polymer chemistry, antimicrobial and antielectrostatic agents, organic synthesis, biomolecular stabilization and activation, and nanoscience. Finally, this review discusses anion-functionalized ILs, including sulfur- and oxygen-functionalized analogs, as well as choline-based deep eutectic solvents (DESs), an emerging class of fluids which can be sensibly categorized as semi-molecular cousins to the IL. Finally, the toxicity and biodegradability of ether- and alcohol-functionalized ILs are discussed and cautiously evaluated in light of recent reports. By carefully summarizing literature examples on the properties and applications of oxy-functional designer ILs up till now, it is our intent that this review offers a barometer for gauging future advances in the field as well as a trigger to spur further contemplation of these seemingly inexhaustible and—relative to their potential—virtually untouched fluids. It is abundantly clear that these remarkable fluidic materials are here to stay, just as certain design rules are slowly beginning to emerge. However, in fairness, serendipity also still plays an undeniable role, highlighting the need for both expanded in silico studies and a beacon to attract bright, young researchers to the field (406 references).

Recently, there is a rising interest in dissolving a variety of carbohydrates (such as sugars, starch and cellulose) in ionic liquids (ILs). The solutions of carbohydrates are then conveniently subject to chemical or physical modifications. However, one serious disadvantage of these ILs is their strong tendency in denaturing enzymes. This drawback prohibits the dissolved carbohydrates from being transformed by enzymatic reactions. In the present study, we designed a series of ILs that are able to dissolve carbohydrates but do not considerably inactivate the immobilized lipase B from Candida antarctica. These ILs consist of glycol-substituted cations and acetate anions. They could dissolve more than 10% (wt) cellulose and up to 80% (wt) D-glucose. The transesterification activities of the lipase in these ILs are very comparable with those in hydrophobic ILs. The hydrogen-bond forming anions, oxygen-containing cations, and low cation bulkiness promote the carbohydrate dissolution, while the low anion concentration appears essential for the enzyme stabilization. Therefore, an optimization could be achieved through a fine design of IL structures. To demonstrate the potential applications of these ILs, we performed the enzymatic transesterifications of methyl methacrylate with D-glucose and cellulose, respectively, both fully dissolved in ionic media. In the case of D-glucose, conversions up to 80% were obtained; and in the case of cellulose, conversions up to 89% and isolated yields up to 66% were achieved.