<p>To reduce carbon dioxide (CO₂) emissions, membranes such as poly(ether-block-amide) (PEBA) are utilized; however, their laboratory synthesis and evaluation can be costly and time-consuming. This study employs molecular simulation (MS) to investigate the transport and physical properties of different PEBA membranes, aiming to streamline the synthesis process in order to decrease time and cost. Specifically, the molecular weight and content of poly(ethylene glycol) (PEG) affect the structure and performance of nine PEBA membranes were assessed. It was found that increasing PEG content made the membrane chains more polar, enhancing their interactions and reducing the fractional free volume (FFV). Also, CO₂ diffusivity and radial distribution function (RDF) of CO₂ in the membranes were improved by increasing PEG content in the copolymer. The simulation results corroborate earlier experimental findings for Pebax® 1657 membranes, and the X-ray diffraction results align with these simulations. Notably, the CO₂ permeability values for the copolymer containing 40 wt% of PEG 1000 (<i>P</i>_<i>1000</i><i>-40</i>) and the copolymer containing 40 wt% of PEG 1500 (<i>P</i>_<i>1500</i><i>-40</i>) were 300.6 and 494 Barrer, respectively. The carbon dioxide/nitrogen (CO₂/N₂) selectivity values for <i>P</i>_<i>1000</i><i>-40</i> and <i>P</i>_<i>1500</i><i>-40</i> were 167 and 145.29, respectively. The separation performance results of these two copolymers demonstrate crossing of the 2019 Robeson upper bound. This indicates that these copolymers have excellent separation performance, making them suitable for commercial and industrial applications. Among all samples, <i>P</i>_<i>1500</i><i>-40</i> and <i>P</i>_<i>1000</i><i>-40</i> demonstrated the highest CO₂ permeability (494 Barrer) and CO₂/N₂ selectivity (167), respectively.</p> Graphical Abstract <p></p>