Mixed matrix membranes composed of WS2 nanosheets and fluorinated poly (2,6-dimethyl-1,4-phenylene oxide) via Suzuki reaction for improved CO2 separation

A method of introducing trifluoromethyl group (-CF3) to the polymer backbone by Suzuki reaction was developed to prepare fluorinated polymers for gas separation. The CO2 permeability increased 119% after the -CF3 group was substituted. Tungsten disulfide (WS2), a graphene-like two-dimensional material, was used for first time as an inorganic filler to prepare composite MMMs to separate CO2, N-2 and CH4. The introduction of WS2 nanosheets increases more transport channels for gas molecules, which lead to the permeability and selectivity of MMMs obviously improved in comparison with the pristine FPPO membrane. The CO2/N-2 selectivity and CO2/CH4 selectivity of 10 wt% WS2-FPPO MMMs reached a maximum about 29.6 and 39.4, respectively, with a CO2 permeability of 472 Barrer at 10 psig and 291 K. The best performance of MMMs for CO2/N-2 and CO2/CH4 surpasses the Robeson's upper bound line. The MMMs showed strong stability in long-term observation. The results indicated a new direction for CO2 separation by introducing -CF3 group to polymer and using 2D WS2 nanosheets as nanofiller.