Enhanced CO2 capture performance of mesoporous silica materials with TEPA amine-based deep eutectic solvent: kinetics and mechanism

Abstract

Conventional amine-based sorbents exhibit two major drawbacks: progressive structural deterioration under repetitive CO₂ adsorption–desorption cycling and diminished gas capture efficiency with extended cycle iterations. To mitigate these issues, a new amine-based deep eutectic solvent (DES) containing tromethamine (TrMA) salt as a sterically hindered amine and tetraethylenepentamine (TEPA) was prepared and incorporated into several mesoporous silica materials for CO₂ capture, including SBA-15, SBA-16, MCM-41, and KIT-6. In comparison to SBA-16 and MCM-41 materials, SBA-15 and KIT-6 could maintain their mesoporous structure after incorporation of 50% DES, as revealed by the N₂ sorption analysis. According to the findings, (50%) TrMA-TEAP (1 : 2)/SBA-15 had a higher CO₂ adsorption of 120.8 (mg g⁻¹) than (50%) pure TEAP (1 : 2)/SBA-15 and the other hybrid amine-based DES/mesoporous silica materials at 75 °C under 15% CO₂ balanced N₂. Furthermore, the adsorption index values for (50%) TrMA-TEAP (1 : 2)/SBA-15 and (50%) pure TEAP (1 : 2)/SBA-15 were 94.9% and 92.5%, respectively, demonstrating that amine-based DES showed superior cycle performance, albeit (50%) TrMA-TEAP (1 : 2)/KIT-6 showed an excellent cycling performance by maintaining the original CO₂ adsorption capacity of 97.3%, amongst the other sorbents. Pseudo-first order, pseudo-second order, Vermeulen, Avrami, and fractal-like exponential kinetic models were used to investigate the kinetic adsorption of hybrid sorbents, with the last kinetic model offering the best fitting. The DFT analysis demonstrated that the primary amine and hydroxyl (OH) groups site on the hydrogen bond donor/acceptor (HBA) are more active site in DES, while the hydrogen bond donor (HBD) plays a dominant role in CO₂ adsorption due to possessing more amine active sites, particularly primary amine sites.