Greening water-lean solvents for CO2 capture: replacing toxic 1-methyl-2-pyrrolidone with high-performance eco-friendly cosolvents

Water-lean solvents are promising alternatives to aqueous amines for post-combustion CO2 capture due to their lower regeneration energy. However, the majority of state-of-the-art water-lean solvents rely on 1-methyl-2-pyrrolidone (NMP) as the organic cosolvent, whose reproductive toxicity poses a serious barrier to large-scale deployment. This study proposes a systematic strategy to identify green, low-toxicity replacements for NMP in water-lean solvents. Based on COSMO-RS σ-profile similarity calculation, 20 high-potential candidates were first identified from 2562 organic solvents. Subsequent environmental, health, and safety (EHS) evaluations, combined with physicochemical property filtering, narrowed the selection to two green cosolvents: methylaminoacetaldehyde dimethyl acetal (MAADMA) and 3-methoxy-1-butanol (MOB). These two candidates and NMP were then experimentally validated in combination with three representative amines (EMEA, DMEDA, and DMPDA) at 5 wt% water content. Among all tested systems, the EM-A-5H solvent (30% EMEA/65% MAADMA/5% H2O) showed the best performance, with a remarkable cyclic capacity of 0.86 mol CO2 per mol amine and a regeneration efficiency of 93.6%. Importantly, EM-A-5H achieved a total regeneration energy of 2.20 GJ per t CO2, 41% lower than conventional 30 wt% MEA and 15% lower than the NMP-based counterpart solvent. It also exhibited an excellent stability and satisfactory viscosity over seven absorption–desorption cycles without performance degradation. This work offers a systematic and practical approach for the rational design of eco-friendly, high-performance water-lean solvents for CO2 capture.