Modulating H-bond Strength to Enhance Reactivity for Efficient Synthesis of Cyclic Carbonates with Tetrabutylammonium Iodide-based Deep Eutectic Solvents

Developing a highly efficient and environmentally friendly catalytic system for CO2 cycloaddition reactions is an attractive way to achieve carbon neutrality. In this work, tetrabutylammonium iodide (TBAI) and polyethylene glycol (PEG) were used to produce novel deep eutectic solvents (DESs), which could serve as both solvents and catalysts, displaying excellent activity to synthesis styrene carbonates from CO2 and styrene oxide under metal-free, cocatalyst-free, solvent-free and mild conditions. A detailed study was undertaken on the effects of reaction parameters, recyclability, and substrate scope. Additionally, the H-bond interaction between the substrate and TBAI/PEG(200) was thoroughly investigated using FT-IR and 1H NMR techniques. The synergistic interaction between the two components of the DES, TBAI, and PEG(200), may be the key to the high catalytic activity of this system. The tetrabutylammonium iodide-based system is an innovative strategy for the CO2 cycloaddition with epoxides, achieved by elaborately devising the H-bonds of DESs to enhance reactivity. This provides a novel green strategy for potential industrial applications.