The results are shown in Figure . We measured the neat PSU first, leading to comparable results as reported earlier. As expected, the small gas He has a high permeability through the PSU, while CH 4 is diffusion limited already by the polymer. Incorporated MIL-116(Ga) filler with 5, 10, 15 and 20 wt.% is compared in its performance, showing a clear trend. The He permeability is increased with increasing filler content, while the permeability of CH 4 is decreasing with increasing filler content, giving a trend to high selectivity with higher loading. It must be noted that our data has been collected for a 4:96 He/CH 4 mixed feed gas following process conditions, while all other data referenced comes from 50:50 mixtures. Some literature gas permeation data sets were conducted through constant-volume/variable-pressure apparatus, rendering direct comparison challenging. The comparison table can be found in the Table .