Enhancing the CO2 plasticization resistance of thin polymeric membranes by designing Metal-polymer complexes

[Display omitted] •Metal-polymer complexes are formed via coordination interaction in polymer membranes.•The mechanical strength and thermal stability of the obtained membranes are largely improved.•CO2 plasticization pressure of the metal-polymer complex thin-film membranes is sharply improved from 6 to 27–30 bar.•CO2/CH4 selectivity is remarkably improved from ∼ 37 to ∼ 50 with increasing the pressure from 1 to 15 bar in thin films. Plasticization greatly reduces the separation performance and shortens the service life of the polymer-based gas separation membranes, which is one of the most critical problems to be addressed. This phenomenon becomes more severe in thin films. In this work, metal-polymer complexes were designed in thin polymeric membranes via coordination interaction between transition metal ions and benzimidazole moieties of polyimide to improve the plasticization resistance. The metal-polymer complexes effectively enhanced the interchain interaction and provided abundant open metal sites. The gas permeation results revealed that the CO2 plasticization pressure of the metal-polymer complex thin films was sharply improved from 6 to 27–30 bar. Remarkably, the thin films containing metal-ion coordination demonstrated an enhanced CO2/CH4 selectivity from ∼ 37 to ∼ 50 with increasing the mixed gas pressure from 1 to 15 bar, which was attributed to many open metal sites that strongly enhanced the affinity of membranes to CO2 and yielded the selective CO2 permeation. This work provides a facile and effective strategy for designing plasticization-resistant polymer membranes for efficient CO2 capture.