Effect of pristine and functionalized single- and multi-walled carbon nanotubes on CO2 separation of mixed matrix membranes based on polymers of intrinsic microporosity (PIM-1): a molecular dynamics simulation study.

Molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations were conducted to investigate the transport properties of carbon dioxide, methane, nitrogen, and oxygen through pure and mixed matrix membranes (MMMs) based on polymers of intrinsic microporosity (PIM-1). For this purpose, first, 0.5 to 3 wt% of pristine single-walled carbon nanotube (p-SWCNT) and multi-walled carbon nanotube (p-MWCNT) were embedded into the pure PIM-1, and then for better dispersion of CNT particles into the polymer matrix and to improve the performance of the resulting MMMs, polyethylene glycol (PEG) functionalized SWCNT and MWCNT (f-SWCNT and f-MWCNT, respectively) were loaded. The characterization of the obtained MMMs was carried out by using density, glass transition temperature, X-ray pattern, and fractional free volume calculations. Comparing the obtained results with the available reported experimental data, indicate the authenticity of the applied simulation approach. The simulation results exhibit that the pristine and PEG-functionalized CNT particles improve the transport properties such as diffusivity, solubility, and permeability of the PIM-1 membranes, without sacrificing their selectivity. Also, the MMMs incorporated with 2 wt% of the functionalized CNT particles indicate better performance for the CO2 separation from other gases. According to the calculated results, the highest permeability and diffusivity for CO2 are observed in the [PIM-1/f-SWCNT] MMM among the other membranes which represent that the loading of the f-SWCNTs can enhance the CO2 separation performance of PIM-1 more than other CNTs studied in this work.