Synergistic Effect of Amino Acid Salt Hybrid Systems for DAC of CO₂

Direct air capture (DAC) is gaining significant global interest as a negative emission technology aimed at controlling atmospheric CO2 concentrations. However, developing a green solvent with low energy demand with the capability of integration with renewable energy resources on a large scale remains challenging. Herein, a wide range of aqueous alkali salts of amino acids at different concentrations were screened for DAC, and their CO2 absorption–desorption performance between 25 and 98 °C was discussed. Sustainable taurine and lysine hybrid solvent was introduced with the aim of enhancing CO2 recovery at a lower regeneration temperature to reduce the cost and energy penalty of aqueous DAC systems. The CO2 cyclic performance of the developed solvent (0.29 mol of CO2 L–1) has demonstrated over a 50% improvement compared to the well-established amino acid salt solvents of sarcosine and glycine (0.18 and 0.19 mol of CO2 L–1, respectively) under the test conditions. We showed that the sulfonic acid group in taurine contributes to exceptionally high thermal stability but reduces its resistance to oxidative degradation compared to the other studied amino carboxylic acids.