Fig. 4: Ion separation performance of COF membranes.

a Salt flux and selectivity of different membranes tested under single-salt conditions (0.1 M for each salt). b Apparent activation energies (\({E}_{a}\)) for electrolyte transport across the COF-TFB, COF-TFB-OMe, and COF-TFB-OH membranes. c Calculated energy barriers for ion transport across the membranes. d Ion flux and selectivity of different membranes under binary-salt systems (0.1 M for each salt). e Comparison of ion flux and selectivity for the COF-TFB-OMe membrane under dialysis and electrically driven conditions in a ternary salt system. f Recyclability test of the COF-TFB-OMe membrane under electro-driven operation over multiple cycles. Error bars in the figures represent standard deviation obtained from three independent experiments using membranes prepared from different batches.