Cyclic secondary amine-based deep eutectic solvents for energy efficient CO2 capture

Global climate catastrophes driven by the greenhouse effect and rising CO 2 emissions highlight the urgent need for improved carbon-capture technologies. Deep eutectic solvents (DESs) have emerged as promising alternatives to ionic liquids and aqueous amines, but few studies assess the energy consumption of CO 2 capture with ternary DESs. The present study synthesized novel ternary DESs using cyclic amines as promoters, which were selected on the basis of their stability, slower consumption, and easier bond cleavage. The CO 2 capture performance of the resulting DESs was then investigated using spectroscopy and molecular dynamics simulations. The DES [ChCl][MEA]-5 %PZ exhibited the highest absorption capacity (0.290 g CO 2 /g), representing a 146 % increase over 30 wt % MEA, and an estimated regeneration efficiency of 88 %. Simulations showed that secondary amines strengthen intermolecular interactions and promote CO 2 uptake, consistent with experimental results. The results of both nuclear magnetic resonance and Fourier-transform infrared spectroscopy analyses indicate that CO 2 reacts with cyclic secondary amines to form carbamates, which enhance capture capacity. The heat of reaction was identified as the main contributor to regeneration energy. It is noteworthy that the regeneration energy for [ChCl][MEA]-5 %IM was 1.79 GJ/t CO 2 , which is approximately 60 % of that for 30 wt % MEA and is comparable to biphasic absorbents. In conclusion, these ternary DESs demonstrate considerable potential for energy-efficient CO 2 capture.