To improve the selectivity of nanofiltration membranes (NFMs) for multi/monovalent anions, including SO₄²⁻/Cl⁻, a strategy to moderately amplify the pore size while maintaining chargeability of the membranes was proposed. Four diamine monomers based on piperazine ring, with reaction site distance increased from 2.8 Å to 5.1 Å, were adopted and the effect of the monomer structure especially the reaction site distance on the structure and performance of the NFMs was studied. Position annihilation spectroscopy and molecular dynamics simulation were adopted to provide thorough characterization of the separation layer of the NFMs. The results showed that NFMs prepared by monomers with moderately increased reaction site distance displayed a moderately amplified pore size, which could facilitate the penetration of Cl⁻ and thus improve SO₄²⁻/Cl⁻ separation ability. The Na₂SO₄/NaCl selectivity got 10.0 with water permeability up to 18.5 L m⁻² h⁻¹ bar⁻¹, exceeding the upper-bound of permeation flux and Na₂SO₄/NaCl selectivity of membranes prepared by traditional interfacial polymerization.

提高纳滤膜 (NFM) 对多价/单价阴离子的选择性，包​​括 SO ₄ ²⁻ /Cl ⁻, 提出了一种在保持膜的充电能力的同时适度放大孔径的策略。采用四种基于哌嗪环的二胺单体，反应位点距离从2.8 Å增加到5.1 Å，研究了单体结构特别是反应位点距离对NFMs结构和性能的影响。采用位置湮没光谱和分子动力学模拟来全面表征 NFM 的分离层。结果表明，由适度增加反应位点距离的单体制备的 NFM 显示出适度放大的孔径，这可以促进 Cl - 的渗透，^从而提高 SO ₄ ^2- /Cl ^-分离能力。Na ₂ SO ₄ /NaCl选择性达到10.0，透水率达到18.5 L m ⁻²  h ⁻¹  bar ⁻¹ ，超过传统界面聚合制备膜的渗透通量和Na ₂ SO ₄ /NaCl选择性上限.