Thin film nanocomposite membranes of superglassy PIM-1 and amine-functionalised 2D fillers for gas separation

Abstract

Loss of free volume over time (i.e. aging) is the main hurdle towards the commercial use of super glassy polymers for gas separation membranes. Aging takes place at a much faster rate in polymeric thin films, with permeability reductions of over 50% in only a few days. In this work 2D reduced holey graphene oxide (rHGO) nanosheets containing amine groups were added into thin films of the super-glassy polymer of intrinsic microporosity PIM-1. At filler loadings of 1 wt% of rHGO-tris(4-aminophenyl)amine, the CO₂ permeance after 1 year of physical aging was 846 ± 37 GPU, which remained very close to that of the fresh membrane tested right after preparation (1050 ± 70 GPU), and was double that of 1 year-aged purely PIM-1 thin film composite membranes (432 ± 4 GPU). Membranes with lower filler concentrations of 0.1 wt% showed CO₂ permeance values of 604 ± 34 GPU after 1 year of aging, but they aged quite rapidly; the initial CO₂ permeance values of the fresh thin film nanocomposite (TFN) membrane at filler loading of 0.1 wt% was 3351 ± 662 GPU. The aging behaviour was also investigated in several tens of micrometres thick membranes (up to 2 years) for filler loadings of 0.1 wt% and the gas separation performance showed similar tendencies to that of thin films; leading to higher CO₂ permeability without sacrificing CO₂/CH₄ selectivity.