Engineering nanoporous block copolymer membranes for fast molecular elimination

Block copolymers (BCPs), promising materials for next-generation membranes, face unprecedented challenges in water purification due to the difficulty in processing them into nanoporous membranes with pores <2 nm—a key barrier for molecular elimination. While recent progress in tailorable pore chemistry offers a solution, an indiscriminate method to remove nonspecific molecules from water remains urgent. To address this, we developed BCP-Fc catalytic membranes with an average pore diameter of 23.4 nm by functionalizing nanoporous BCP membranes with ferrocene (Fc). These membranes removed 96% of Rhodamine B (RhB) while maintaining a permeance of 750 L/(m 2 ·h·bar), comparable to other state-of-the-art membranes. The effect of pH on removal efficiency and permeance was also examined. The membranes effectively eliminated the positively charged dyes of methyl blue (MB), crystal violet (CV), and neutral red (NR) with the efficiencies of 96.6%, 93.6%, and 99.1%, respectively, and the negatively charged dyes of methyl orange (MO) and acid red 73 (AR 73) with efficiencies of 74.6% and 74.2%, respectively. Moreover, the membranes maintained high elimination efficiencies for dye mixtures. The membranes demonstrated continuous operation for up to 38 h and superior reusability. The molecular elimination mechanism was further revealed. This work presents an innovative strategy for custom-tailored BCP membranes, enabling fast molecular elimination.