Fig. 4: Stability and durability of the QL-COF-2 and LZU-1 membranes.

a Long-term stability of QL-COF-2 membranes under 50 ppm CR solutions. b The images of QL-COF-2 and LZU-1 membranes before and after treatment in 1 M HCl and 1 M NaOH. Nanofiltration performance of QL-COF-2 (c) and LZU-1 (d) membranes under harsh treatment.