This effect was further corroborated by the concentration-dependent conductance of K + in the concentration range of 10 -7 to 1 M. The ion flux exhibited a plateau at low salt concentrations (<10 -5 M), whereas UiO-66 showed a near-linear relationship with salt concentration (Figure ), indicating the contribution of charge from the amino group of UiO-66-NH2 compared to UiO-66 (Supplementary note 10).