fig3

Figure 3. pH-gated ion transport in TpPa-based COF membranes. (A) Conductance at 10^-6 M KCl as a function of pH for the four membranes. Reversible conductance switching (B) between pH 7 and pH 3, and (C) between pH 7 and pH 11.5 at 10^-6 M KCl. Shaded areas indicate the fluctuation range over consecutive cycles; (D) Apparent surface charge density (σ) calculated from ζ potential measurements as a function of pH; (E) Zero-current potential of the four COF membranes at pH 7. Error bars in (A) and (E) represent the standard deviation obtained from three independent measurements for each sample and condition. COF: Covalent organic framework.