Fig. 5. Mixture fitting and graded sieving using a single switchable membrane.
a, BB rejection in mixtures of water and MeOH (v/v) for CC3-PAN (top), and photographs of the permeates (bottom). All error bars depict the s.d. of the data points obtained from at least three independent membranes. The red dashed line was fitted as the logistic function (y = 1/(1 + exp(−16.1(x – 0.617))); Supplementary Section 1.4). b, Photographs showing the ternary molecular separation in a filtration dead-end cell, the nascent mixture feedstock, the permeate (P) collected in the first and second step, and the retentate (R) collected in the second step. c, Scheme showing ternary molecular separation of three dyes (DR, BB and NP) using one single membrane (CC3-PAN) in a continuous process: Step 1, CC3α-PAN in water (blue background) allows permeation of only NP, leaving BB and DR in the retentate. Step 2, 90 vol% MeOH (green background) was added into the retentate to transform the membrane structure to CC3γ′-PAN, which allows permeation of only BB, leaving DR in the retentate. d, Ultraviolet–visible absorption spectra of the mixture containing three molecules in water, permeate from water, mixture and permeate from 90 vol% of MeOH in water and the remaining retentate. Note, the maximum absorbance wavelength for BB is 551 nm in water and 587 nm in MeOH; BB also shows absorbance at 305 nm in MeOH, while NP shows its maximum absorbance at 312 nm in the same solvent.