Pyrrole/MXene membranes with simultaneously high structural stability and permeability for nanofiltration: Implication for water transport

Laminar MXene membranes hold great promise for aqueous separation applications. However, their susceptibility to oxidation in water cause chemical degradation and functional loss, impeding their separation efficiency and durability. In this study, an enhanced MXene nanofiltration membrane was fabricated by simply incorporating pyrrole with Ti3C2Tx, resulting in significantly improved oxidation resistance and permeability. Compared with pure MXene membrane, the pyrrole/MXene membrane exhibited a 3.52-fold increase in water permeance (465.9 L m−2 h−1 bar−1) and achieved excellent rejection performance for various dye molecules. The molecular dynamics simulations revealed that the pyrrole/MXene system presented a higher diffusion coefficient due to the weaker interaction energy at the interface between water molecule and pyrrole/MXene membrane. Normally, a larger transmembrane energy barrier meant a higher transport resistance that prevented the molecule from passing through the membrane. In this way, the determination of activation energy showed that the introduction of pyrrole facilitated a reduction in the requisite activation energy of water transfer from 9.37 to 4.86 kJ mol−1. More importantly, we explored the fact that the stabilization of MXene membranes had a significant impact on their separation performance during a long-term operation. Compared with pristine MXene membrane, the pyrrole/MXene membrane maintained initial two-dimensional structure and stable nanofiltration performance after prolonged operation. The radial distribution function calculations demonstrated that the chemical interactions between Ti3C2Tx and pyrrole were strong and involved the formation of Ti–C bonding and intermolecular interaction. This research provides a facile and effective method to prepare a high-performance and stable MXene nanofiltration membrane.