Effect of chain length of functional groups on the water desalination performance of BDF-COF-An multilayer membrane

MJ Guan and DF Yang and Q Li and MM Cai and LY Wu and QZ Liu, JOURNAL OF MEMBRANE SCIENCE, 733, 124335 (2025).

DOI: 10.1016/j.memsci.2025.124335

The properties of functional groups can be modified by adjusting their composition, which significantly impacts the desalination performance of covalent organic framework (COF) membranes. However, the effect of chain length of functional groups on seawater desalination performance of COF membrane has been infrequently investigated. In this study, molecular dynamics simulations were conducted to explore the influence of chain length on the desalination performance of COF membranes. The simulation results indicated that the conformational evolution of the groups exhibited a significant layer-chain length synergy effect. Among them, the medium and long chain systems (A4, A6) induced the topological reconstruction of the nanochannels through the interlayer close-packing effect and dynamically regulated the transport path of water molecules within the membrane pores. The water permeance of COF membrane increased and decreased with the group chain length, and it was found that in the case of eclipsed stacking, the water permeance of the (n+2) layer BDF- COF-An (An, n represents the number of n atoms in the long-chain group) membrane combinations were similar to those of the n layer A(n+2) membrane combinations. The increase in chain length led to a decrease in both ion flux and water flux, while the difference in the reduction of the two resulted in different in-pore transport effects of various An membranes. Hence, the ion rejection rate of An membranes did not exhibit a continuous upward trend with increasing chain length. The varying entanglement degrees of the different chain lengths of the groups resulted in significant differences in the transport effects in the membrane pore channels, leading to different desalination performance of COF membranes. This work elucidated the mechanisms through which functional group chain length influenced the seawater desalination performance of COF membranes, which might offer valuable insights for the advancement of COF-based desalination technologies.

Return to Publications page