Implicit solvent effects on the binding interactions of amines with CO₂

CO₂ capture and storage using amine-based solvents is a widely explored strategy in the literature aimed at mitigating the environmental impact associated with large-scale fossil fuel combustion. In the present work, four amines with distinct basicity levels were modeled in fifteen solvents with dielectric constants ranging from 1.88 (hexane) to 111 (formamide), in order to assess which implicit solvation approach, PCM, CPCM, or SMD, provides co-solvation results in closer agreement with theoretical and experimental data reported in the literature. A comprehensive analysis of implicit solvation effects was conducted, examining both the structural consequences of CO₂ capture and the variations in stabilization energies associated with the formation of the zwitterionic intermediate. The results indicate that the SMD solvation model exhibits trends more consistent with literature data, owing to its sensitivity to local solute-solvent interactions, particularly hydrogen bonding. Notably, the SMD parameterization incorporates hydrogen-bond acidity and basicity descriptors derived from the Abraham solvation model, enabling correlation analyses between these parameters and the thermodynamic and solvation quantities. These findings provide deeper insight into the fundamental role of co-solvation in CO₂ capture by amine-based solvents, particularly in reducing the free energy of stabilization of the zwitterionic state. Furthermore, this study identifies the implicit solvation approach that, when combined with DFT, yields result most consistent with established theoretical and experimental benchmarks reported in the literature.

All calculations were performed at the DFT CAM-B3LYP/6-311++G(d,p) level of theory.