Fig. 1

Schematic illustration of GCN functionalization for selective permeation. a Precise interlayer distance control of protonated GCN with desired functionalities via anion intercalation strategy. R-SO₃ represents the anion of Brønsted acid or chiral organic acid, sulfate or (1R)-(-)-10-camphorsulfonate anion is utilized in this work. Orange, blue and azure balls in R-SO₃ denote S atom, O atom and remaining group in acid, respectively. Pink, dark blue and light yellow balls in GCN framework denote N atom, C atom and proton, respectively. b Sieving effect of solutes with different sizes over GCN-SA membrane. Light blue ellipse, pink and light blue balls denote large, big and small molecules, respectively. The yellow spring denotes the interlayer space in-between protonated GCN layers. c Enantioselective permeation effect of different enantiomers over GCN-CSA membrane. The yellow spiral denotes the chiral sites created in-between protonated GCN layers, the left and right hands denote a pair of enantiomer for enantioselective permeation. The arrows in b and c denote the permeation direction of various solutes