Design, synthesis, and fixed-bed evaluation of CO₂-selective molecularly imprinted polymers via DFT and RSM approaches

The study of methods to capture carbon dioxide (CO2) from major emission points and prevent its uncontrolled release into the atmosphere has grown significantly. Therefore, it is essential to develop selective and efficient adsorbents for CO2 removal. Molecular imprinting technology makes specific “molecular keys” through preassembling, polymerizing monomers, cross-linking agents, and eluting template molecules. In this study, methacrylamide, identified as the optimal functional monomer with the highest affinity for CO2 among five nitrogen (N2) rich monomers, was quantitatively selected using density functional theory calculations. Utilizing computational molecular simulations, molecularly imprinted polymers (MIPs) were successfully synthesized via the precipitation polymerization method for CO2 removal. The parameters for polymer synthesis were further optimized by employing response surface methodology coupled with central composite design. Three mmol of monomer, 20 mmol of cross-linker, and 35 mL of porogenic solvent were reported to be the optimum parameters that resulted in the highest binding capacity. The optimized polymer was further subjected to a series of characterizations. The effect of various adsorption process parameters (temperature, flow rate, and CO2 concentration) on CO2 adsorption in a fixed bed was also investigated. The adsorption data fitted the Langmuir model for isotherm analysis, the Avrami model could explain the kinetic behavior of the adsorbent, and the Yoon-Nelson model described the column adsorption behavior. The MIP indicated a high selectivity for CO2 over N2 gas, and the regeneration study reported a minimal reduction in adsorption capacity of approximately 8% even after the 10th cycle. This research suggests that the synthesized MIP shows potential for CO2 removal with high selectivity and good reusability. In addition, the application of computational research has also promoted a green synthesis approach, an environmentally friendly approach to the development of MIPs. CO₂-selective MIP synthesized using methacrylamide as the functional monomer. DFT calculations used to screen and select the optimal nitrogen-rich monomer. MIP shows excellent CO₂/N₂ selectivity and stable adsorption after 10 cycles. Adsorption behavior modeled by Langmuir, Avrami, and Yoon–Nelson equation.