بررسي گيراندازي CO2 توسط حلال يوتكتيك عميق اتالين، يك چارچوب آلي كووالانسي LZU-192 و كامپوزيت آن‌ها به روش شبيه‌سازي ديناميك مولكولي

Investigation of CO2 capture by ethaline deep eutectic solvent, a covalent organic framework LZU-192 an‎d their Composite by the molecular dynamic’s simulation method

شيمي فيزيك

The escalating concentration of dioxide carbon (CO₂) in the atmosphere, contributing to global warming, ocean acidification, an‎d severe climate changes, underscores the critical need for efficient an‎d sustainable CO₂ capture technologies. Covalent organic frameworks (COFs), with high adsorption capacity, large specific surface area, an‎d active chemical groups (e.g., nitrogen an‎d oxygen), an‎d deep eutectic solvents (DESs) like ethaline, with biocompatibility, low cost, suitable viscosity, an‎d high gas solubility, have emerged as promising novel adsorbents. Combining these materials into a composite leverages their complementary advantages, mitigating the limitations of individual adsorbents by enhancing adsorption capacity, selec‎tivity, mass transfer, an‎d stability under various operational conditions. This study aims to investigate the CO₂ adsorption capacity of ethaline solvent, COF-LZU-192, an‎d their composite formed by combining ethaline with COF, while analyzing the effects of temperature an‎d concentration. In the first stage, the ethaline + CO₂ system was examined at four temperatures (278, 298, 318, an‎d 338 K) an‎d two concentrations (156 an‎d 312 CO₂ molecules). The second stage involved analyzing the COF-LZU covalent organic framework with CO₂ under the same conditions. In the third stage, the COF-LZU-192 + ethaline composite was developed at three ethaline concentrations (216, 108, an‎d 56 ethaline molecules) to form the composite with the framework. In the fourth stage, CO₂ was introduced to the composite systems at two concentrations to assess the impact of concentration an‎d operational conditions on CO₂ adsorption capacity. All simulations were performed using molecular dynamics in LAMMPS, employing the GAFF force field for ethaline an‎d COF-LZU-192 an‎d the TraPPE force field for CO₂. Force field validation for ethaline an‎d CO₂ was conducted using the NPT ensemble, achieving experimental densities. Subsequent simulations utilized the NVT ensemble. Post-simulation analyses included mean square displacement (MSD) an‎d diffusion coefficients, radial distribution function (RDF), an‎d density profiles to eva‎luate CO₂ adsorption an‎d distribution under varying temperature an‎d concentration conditions. The simulation results revealed that in composite systems, MSD an‎d CO₂ diffusion decreased compared to stan‎dalone systems, indicating greater adsorption stability. Among the three concentrations C1, C2, an‎d C3, the C2 ethaline concentration (108 molecules) established a good balance between viscosity an‎d free space, effectively limiting CO₂ mobility an‎d enhancing adsorption. The presence of COF strengthened ethaline-CO₂ interactions (higher an‎d closer RDF peaks), particularly at C2, increasing adsorption capacity up to twofold. Chloride an‎d ethylene glycol oxygen remained the primary sites, while COF concentrated ethaline in pores, creating a more organized distribution of active centers. RDF comparisons between stan‎dalone an‎d composite systems showed that COF enhanced CO₂ access to chloride an‎d other ethaline groups, improving adsorption capacity. Regarding density profiles in the composite system, adding ethaline altered CO₂ distribution. At the medium C2 concentration, synergy between ethaline an‎d COF significantly increased adsorption in central regions due to strong hydrogen bonds an‎d CO₂ guidance toward pores. Thus, by tuning ethaline concentration relative to COF, superior composite performance over individual adsorbents can be achieved, positioning it as a green, cost-effective, an‎d efficient approach for CO₂ capture an‎d separation. These findings provide a foundation for developing advanced industrial adsorbents with higher efficiency.

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