Ionic liquids and their various analogues are without doubt the scientific sensation of the last few decades, paving the way to a more sustainable society. Their versatile suite of properties, originating from an almost inconceivably large number of possible cation and anion combinations, allows tuning of the structure to serve a desired purpose. Ionic liquids hence offer a myriad of useful applications from solvents to catalysts, through to lubricants, gas absorbers, and azeotrope breakers. The purpose of this review is to explore the more unexpected of these applications, particularly in the energy space. It guides the reader through the application of ionic liquids and their analogues as i) phase change materials for thermal energy storage, ii) organic ionic plastic crystals, which have been studied as battery electrolytes and in gas separation, iii) key components in the nitrogen reduction reaction for sustainable ammonia generation, iv) as electrolytes in aluminum‐ion batteries, and v) in other emerging technologies. It is concluded that there is tremendous scope for further optimizing and tuning of the ionic liquid in its task, subject to sustainability imperatives in line with current global priorities, assisted by artificial intelligence.

Carbohydrate-derived ionic liquids have been explored as bio-alternatives to conventional ionic liquids for over a decade. Since their discovery, significant progress has been made regarding synthetic methods, understanding their environmental effect, and developing perspectives on their potential applications. This review discusses the relationships between the structural properties of carbohydrate ionic liquids and their thermal, toxicological, and biodegradability characteristics in terms of guiding future designs of sugar-rich systems for targeted applications. The synthetic strategies related to carbohydrate-based ionic liquids, the most recent relevant advances, and several perspectives for possible applications spanning catalysis, biomedicine, ecology, biomass, and energy conversion are presented herein.

Dicationic and tricationic ionic liquids, synthesised by proton transfer from sulfuric acid and corresponding di- and triamines, were characterised and used as Brønsted acidic catalysts in biodiesel production.

The growing interest in the application of ionic liquids (ILs) with simultaneous sustainability draws attention to their environmental impact in general and their biodegradability in particular. Considering this, we designed a series of novel bio-ionic liquids based on natural, abundant compounds: a carbohydrate [Carb], as the cation, and amino acids [AA], as the anions; these ILs can serve as viable alternatives to the well-known and utile cholinium AAILs. Several [Carb][AA] ILs were characterized by ¹H and ¹³C NMR, mass spectrometry, thermogravimetry (TGA) and differential scanning calorimetry (DSC). The biodegradability properties of the [Carb][AA] ILs were elucidated as well and showed biodegradation readily occurred, decomposing within 5–6 days. These novel materials were successfully utilized as catalysts for the Knoevenagel condensation reaction, where conversion values of 67–94% were achieved under exceptionally mild conditions using water as the solvent and reaction times as short as 15 minutes. These sugar based ILs were easily separated and recycled.