For this, we visualize a particular system, C 3 polymer with ϕ s = 0.43 in Fig. . We note here that this structure has a somewhat higher fraction of solid lattice sites, and we employ this structure to emphasize and illustrate the topological effects. While in general, the fraction remaining available vacant lattice sites is below the percolation threshold for square lattice, we checked that the particular matrix realizations employed remain percolated with respect to fluid transport. The top panel in Fig. shows the local flux (J l,l+1 A ) distribution in the direction of fluid flow, and the bottom panel demonstrates the local selectivity difference (∆ α A/B ) where the local selectivity (α local A/B ) is calculated from the following equation: