Molecular simulations of Poly-4-methyl-1-pentene (PMP) and PMP/Calix[4]arene (PMP/CA) for H2S/CO2 separation

Efficient separation of H${}_2$S and CO${}_2$ is crucial for industrial applications. Poly-4-methyl-1-pentene (PMP) membranes, enhanced with Calix[4]arene (CA), show promise in improving separation performance. Herein, Molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulations were used to systematically investigate the gas transport properties of H${}_2$S over PMP membranes, as well as the performance of mixed matrix membranes (MMMs) with varying CA contents (0–7.75 wt%) in H${}_2$S/CO${}_2$ gas separation. The results indicate that while CO${}_2$ exhibits a higher diffusion coefficient than H${}_2$S, it has a lower solubility coefficient and permeability coefficient, suggesting that the permeation process is predominantly governed by solubility. The incorporation of CA significantly enhances the H${}_2$S/CO${}_2$ separation performance. Notably, the 7.75% CA-doped M5 system exhibits a 93.6% increase in separation factor ($\alpha =4.28$) compared to pure PMP ($\alpha =2.21$). In addition, CA doping significantly improves the thermal stability, with the glass transition temperature ($T_g$) of M5 rising by 25%, and mechanical properties, as evidenced by a 12.4% increase in Young’s modulus. These findings highlight the dual role of CA in modifying both the thermodynamic and kinetic properties of PMP membranes. In summary, this study provides a theoretical basis for the application of PMP-based composite membranes in gas separation and important guidance for material optimization.