1-Butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide, often short-handed as BMIM-TFSI, lands as a prominent ionic liquid in both chemical research and industry. A core part of its appeal comes from its unusual combination of high thermal stability, strong solubility profile, and its almost total lack of odor or noticeable vapor, which points to a very low volatility. In simplest terms, this material blends a butyl-methylimidazolium cation — a five-membered heterocycle with alkyl side groups — and a bis(trifluoromethanesulfonyl)imide anion, which showcases highly delocalized charge and notable electron-withdrawing trifluoromethyl groups. The molecular formula stands as C8H15F6N3O4S2.
My direct experience with BMIM-TFSI as both a raw material in research labs and as a specialty solvent lets me underline the variety it shows in physical form. The compound often arrives as a colorless to pale yellow transparent liquid at room temperature, though at lower temperatures or in certain purities, users can find it forming crystals or a waxy solid. Its density sits near 1.43 g/cm³, which is heavier than water in the same volume. The liquid pours syrupy, reminding me of heavy oils, but still moves quickly enough not to gum up routine glassware. Commercial types sometimes appear as flakes, powder, solid pearls, or as a crystal batch, depending on manufacturer requirements and storage conditions. When supplied as a solution, BMIM-TFSI keeps stable and dissolves a remarkable variety of organic or inorganic compounds, making it a solid choice for tough extraction or catalysis applications.
From extensive lab use, I’ve learned that BMIM-TFSI rarely disappoints when safe handling and chemical inertness are required. The combination of the imidazolium cation and the TFSI anion delivers an ionic liquid with almost no measurable vapor pressure at room conditions. This nearly eliminates fire hazards linked to explosive vapor, which remains a risk with volatile organic chemicals. The temperature window for liquid phase spans from well below zero Celsius up to about 400°C before thermal decomposition, beating many typical solvents. BMIM-TFSI’s hydrophobic character stands out: water doesn’t mix well, but polar and non-polar organics blend easily. Its high ionic conductivity also sets it apart in battery research and electrochemistry. High chemical resistance means it endures strong acids and bases in ways simple organic solvents can’t. In electroplating, separating rare earth metals, or as a base for making stable, non-corrosive lubricants, the material’s unique properties have found real, practical use.
Anyone considering the use of BMIM-TFSI as a raw material must look closely at both its chemical and toxicological profiles. Unlike some solvents and reagents that evaporate or break down quickly, ionic liquids like this one tend to persist in the environment. While BMIM-TFSI carries a relatively low acute toxicity rating by oral or dermal exposure, it isn’t totally benign. Prolonged skin or eye contact can irritate; laboratory wisdom recommends gloves and splash goggles for everything above a minute of handling. There is emerging research into chronic hazards, especially concerning aquatic ecosystems — ionic liquids resist breakdown and may bioaccumulate under some circumstances. Disposal often requires solvent waste collection, and regulatory guidance can shift as more long-term studies complete. The material’s HS Code, which sits under 2921.29.90, reflects its chemical category as an organic compound containing a heterocyclic structure with nitrogen atoms. Those working daily with this chemical appreciate suppliers who provide detailed safety data sheets and, more importantly, transparent sourcing information so risk management isn’t left up to guesswork.
Specifications for BMIM-TFSI hinge on purity: top-grade product reaches above 99% by weight, with tightly controlled traces of halides and silicates since these can ruin experiments in sensitive fields like analytical chemistry or nano-manufacturing. Viscosity, water content, and conductivity also find themselves as defining technical specs. In day-to-day use, BMIM-TFSI often functions as a safe replacement for traditional organic solvents in high-value applications — such as battery electrolytes, chemical separation science, and green catalysis. Manufacturers typically offer the material in liter-scale glass or HDPE bottles for labs, or larger jerricans for industry, adjusting packaging to avoid moisture and light exposure that might degrade its quality. For researchers, insight into the subtle interplay between cation and anion structure helps tweak and optimize reactions; for chemical producers, reliability and batch consistency stay vital for keeping downstream customers happy and processes reproducible.
The biggest challenges with BMIM-TFSI meet at the intersection of cost and environmental management. The material demands relatively complex and energy-intensive synthesis, which drives up price for research chemists looking to use it in bulk—or for companies scaling production for demanding applications like next-generation batteries. There’s also the problem of how readily it enters water streams, since ionic liquids have a way of sticking around in ways simple alcohols do not. Direct experience in the lab pushes home the need for closed systems—fume hoods, containment trays, and neutralizing agents available at arm’s length are practical, necessary measures for responsible use. Solutions include investing in better purification techniques, promoting recycling and re-use within chemical plants, and supporting open access research to fully map the compound’s environmental footprint. Above all, clear communication about handling, hazards, and end-of-life treatment between producers and users forms the backbone of effective risk management and sustainability.
