A series of chemically functionalized porous aromatic frameworks (PAFs) have been synthesized and deployed within mixed-matrix membranes for gas separation. This series of PAFs delivered for the first time simultaneous control of selective gas transport and physical aging within the membranes. New composites including native and metalated fullerenes were also prepared, and the composites exhibited exceptional increases in their porosity, which in turn resulted in ultrafast gas transport. CO2 permeability following PAF-1-Li6C60 infusion within poly(trimethylsilylpropyne) was as high as 50 600 Barrer, a 70% improvement. Remarkably, just 9% of this permeation rate diminished after 1 year of physical aging, compared to 74% in the native polymer. A series of characterization techniques revealed this phenomenon to be due to intercalation of polymer chains within the PAF pores, the strength of which is controlled by the levels of chemical functionalization and porosity. The membranes were exploited for gas separations, in particular the stripping of CO2 from natural gas.