Superhydrophilic Sub-1-nm Porous Membrane with Electroneutral Surface for Nonselective Transport of Small Organic Molecules

The study of traditional Chinese medicines (TCMs) is receiving increasing attention worldwide because of their contribution to human health. Developing an effective and sustainable method for screening TCMs is highly desired to accelerate the modernization of TCMs. In this work, we report a neutrally charged membrane made of a positively charged polyelectrolyte electrostatically assembled on a negatively charged superhydrophilic nanoporous membrane. The composite membrane possesses stable electroneutrality in a wide pH range and can precisely and nonselectively separate various charged molecules in TCMs with a transmittance higher than 90% for molecules with molecular weight (M-w) < 400 and a high rejection of 90% for molecules with M-w > 800. In addition, the membrane exhibits a superior antifouling performance, and the recovery ratio observed during a continuous cycling test of a simulated TCM solution was more than 93%. The combination of superhydrophilicity and electroneutrality in a nanoporous membrane provides a new route for designing nanofiltration membranes for highly efficient molecule separation and is promising for screening TCMs.