Imidazolium-based ionic liquid immobilized on functionalized magnetic hydrotalcite (Fe3O4/HT-IM): as an efficient heterogeneous magnetic nanocatalyst for chemical fixation of carbon dioxide under green conditions

Abstract

A reusable, eco-friendly, long-lived and efficient nanocatalyst, imidazolium-based ionic liquid immobilized on functionalized magnetic hydrotalcite (Fe₃O₄/HT-IM, IM is known as imidazolium-based melamine), was successfully introduced. The structure of the synthesized nanocatalyst was characterized by several techniques which revealed a plate-like shape with an average particle size of approximately 50 nm and also the presence of acidic sites (site density: 12 mmol g⁻¹). The catalytic activity of Fe₃O₄/HT-IM was explored in the chemical fixation reaction of carbon dioxide towards the preparation of cyclic carbonates under optimized reaction conditions at 100 °C, 0.7 MPa and 1.6 mol% of the nanocatalyst. This reaction was conducted without using any metal, additive, toxic reagents and solvent/co-catalyst which provides mild and green conditions from the standpoint of green chemistry. Owing to having acidic-basic sites which can simultaneously accelerate the ring-opening of the epoxy ring and incorporation of CO₂, this catalyst is attractive and suitable for this reaction. In particular, the prepared catalyst can be easily separated using an external magnetic field and reused over six times without any significant loss in catalytic performance and selectivity. This proves its great potential to be implemented for industrial purposes as a green catalyst.