Have a Cake and Eat it Too: A Nanofluidic Hybrid Membrane with Both High Stability and Ionic Conductivity

Abstract Two‐dimensional nanofluidic membranes are promising candidates for various applications, such as energy conversion and ionic sensing. However, simultaneously achieving high stability and high ion transport in a nanofluidic membrane remains a great challenge. Herein, a robust and durable aramid nanofiber/carboxylated aramid nanofiber (ANF/cANF) nanofluidic hybrid membrane is designed with high ion conductivity and selectivity via surface grafting engineering and hybridization strategies. Due to the inherent ordered and asymmetric molecular structure, the strong interchain interactions of the ANF and the strong interfacial interactions between the ANF and cANF enable the membrane to exhibit robust structural stability in a wet state. Meanwhile, the enhanced surface charge enabled by the surface functionalization of carboxyl groups on the ANF results in excellent ion transport. As a result, the conductivity of the membrane is 5 and 36 times higher than the ANF membrane and bulk solution, respectively. Importantly, the ionic conductivity and mechanical strength of the membrane remain unchanged even after immersing in water for 90 days, demonstrating favorable underwater application potential. Moreover, the membrane is recyclable and has superior processability, allowing for large‐scale processing. This work provides a new strategy for designing durable and high‐ion‐transporting nanofluidic membranes for ion sensing and energy conversion.