Electronic-Structure-Guided Screening of Piperazine Derivatives: Achieving Efficient CO₂ Capture with High Cyclic...

Piperazine (PZ) is a promising alternative to monoethanolamine (MEA) for CO₂ capture, yet its low desorption efficiency restricts practical implementation. Here, a density functional theory (DFT)-driven framework is developed to identify PZ derivatives with improved performance. By integrating electronic descriptors-including molecular electrostatic potential (ESP) for absorption capacity, ESP at hydrogen nuclei (ESP_H) for desorption efficiency, activation barrier (ΔG‡) and Gibbs free energy change (ΔG) for absorption rate, and interaction-region indicator (IRI) for energy consumption-the key performance of the derivatives is predicted. Experimental validation confirms the framework's predictive accuracy, with 2,6-dimethylpiperazine (26DMPZ) identified as an optimal candidate. It demonstrates a desorption amount of 0.72 mol mol^-1-amine (≈80% higher than PZ), due to more negative ESP_H values. Furthermore, it shows 31% lower energy consumption compared to MEA, attributed to unstable dicarbamate formation. Spectroscopic analyses and solvation free energy calculations reveal that the low-solubility of this dicarbamate salt further enhances CO₂ capture performance without requiring organic solvents. Notably, the system retains 98.4% of its initial cyclic capacity over 10 rapid absorption-desorption cycles, indicating the industrial application potential. This study establishes an electronic-structure-guided screening strategy for amine solvents, highlighting precipitation-driven phase separation as a tunable mechanism to optimize CO₂ capture performance.