一种阴离子型共价有机框架薄膜材料的制备及其锂镁离子分离性能

Two-dimensional covalent organic frameworks (COFs) membranes are ideal materials for molecular separation. In this paper, a 2D COF membrane, TpPa-SO₃H, was rapidly prepared on a porous aluminium oxide(AAO) substrate by in situ solvent-thermal polymerization using 2,4,6-trihydroxy-1,3,5-benzotricarboxaldehyde(Tp) and 2,5-diaminobenzenesulphonic acid (Pa-SO₃H) as the building monomers, and the separation performance of the resulting membrane for lithium and magnesium ions was investigated. The results showed that the membrane surface was smooth and dense with high crystallinity and one-dimensional nanopores. The negatively charged sulfonic acid groups were not only conducive to the improvement of the permeation flux of the membrane, but also enhanced the separation efficiency of the two ions through electrostatic interactions. The separation factor of this membrane for Li⁺/Mg²⁺ in a binary salt system of LiCl (0.1 mol/L) and MgCl₂ (0.1 mol/L) was up to 22. Electrostatic and hydrogen bonding interactions are the main diffusion resistance of magnesium ions in COF membranes and the decisive influences on the ion separation properties.