Natural deep eutectic solvents (NADES) derived from choline chloride and indole-3-butyric acid for optimized CO2 utilization through cycloaddition with epichlorohydrin

Abstract

The transition to a sustainable chemical industry necessitates the development of environmentally friendly solvents and catalysts. Carbon dioxide utilization reactions offer a promising avenue for reducing greenhouse gas emissions, but their commercialization depends on the availability of green catalysts and solvents. Traditional options often suffer from toxicity, volatility, and flammability, hindering their industrial application. Natural deep eutectic solvents (NADES) present a sustainable alternative. This study explores the potential of NADES derived from choline chloride (ChCl) and indole-3-butyric acid (IBA) as catalysts for the cycloaddition of CO₂ with epichlorohydrin. Nine NADES compositions were prepared and characterized using FTIR, NMR, DSC, and TGA. The [ChCl] : [IBA] (0.8 : 0.2) mixture exhibited the lowest melting point (4.4 °C) and the highest catalytic activity (TOF = 1091 h ¹). Under optimized conditions, the catalyst demonstrated excellent reusability, maintaining its activity over four catalytic cycles.