Highly stable and anti-swelling two-dimensional (2D) MXene (Ti₂C₃T_x) membranes can be applied for ion sieving and water purification under external voltage. This paper shows the effective ion sieving of mixed K⁺/Pb²⁺ pairs and the high rejection of the heavy metal ions (Pb²⁺) through a thermal cross-linked 2D MXene membrane by exerting external voltage. Due to the dehydration and cross-linking of hydroxyls during the drying process, the interlayer spacing of MXene membrane is tuned to be 6.7 ~ 6.92 Å, which lies in the selective ion sieving size of the mixed K⁺ and Pb²⁺. The rejection of hydrated Pb²⁺ is up to 99%, while the hydrated K⁺ can smoothly transport the channels of MXene membrane under external voltage. For 365-nm-thick MXene membrane, the separator factor of mixed K⁺ and Pb²⁺ reaches up to 78 under an applied voltage of 16.5 V. Furthermore, the application of external voltage doesn’t result in swelling of MXene membrane, showing stable separation of K⁺/Pb²⁺ pairs with effective rejection of Pb²⁺. The high rejection of Pb²⁺ and good anti-swelling demonstrate the stability of the resultant MXene membranes. Our work indicates that the thermal cross-linked MXene membrane is a promising alternative for ion sieving and the rejection of heavy metal ions.

高度稳定且抗溶胀的二维（2D）MXene（Ti ₂ C ₃ T _x）膜可用于在外部电压下进行离子筛分和水净化。本文展示了有效的K ⁺ / Pb ²⁺混合对离子筛分和重金属离子（Pb ²⁺）通过热交联二维MXene膜施加外部电压的高截留率。由于在干燥过程中羟基的脱水和交联，MXene膜的层间距调整为6.7〜6.92Å，这取决于混合K ⁺和Pb ²⁺的选择性离子筛大小。水合Pb ²⁺的排斥高达99％，而水合的K ⁺可以在外部电压下平稳地传递MXene膜的通道。对于厚度为365 nm的MXene膜，在16.5 V的施加电压下，混合的K ⁺和Pb ²⁺的分隔系数达到78。此外，施加外部电压不会导致MXene膜膨胀，这表明稳定分离K ⁺ / Pb ²⁺对，并有效排斥Pb ²⁺。Pb ²⁺的高抑制率良好的抗溶胀性证明了所得MXene膜的稳定性。我们的工作表明，热交联的MXene膜是离子筛分和重金属离子排斥的有前途的替代方法。