Two-dimensional MXene membranes with biomimetic sub-nanochannels for enhanced cation sieving

Membranes with fast and selective separation of ions are universally desired in many applications. Here, authors inspired by biological potassium ion channels have constructed an MXene based biomimetic ion channel membrane to achieve efficient separation of ions. Membranes with high ion permeability and selectivity are of considerable interest for sustainable water treatment, resource extraction and energy storage. Herein, inspired by K+ channel of streptomyces A (KcsA K+), we have constructed cation sieving membranes using MXene nanosheets and Ethylenediaminetetraacetic acid (EDTA) molecules as building blocks. Numerous negatively charged oxygen atoms of EDTA molecules and 6.0 & ANGS; two-dimensional (2D) sub-nanochannel of MXene nanosheets enable biomimetic channel size, chemical groups and tunable charge density for the resulting membranes. The membranes show the capability to recognize monovalent/divalent cations, achieving excellent K+/Mg2+ selectivity of 121.2 using mixed salt solution as the feed, which outperforms other reported membranes under similar testing conditions and transcends the current upper limit. Characterization and simulations indicate that the cation recognition effect of EDTA and partial dehydration effects play critical roles in cations selective sieving and increasing the local charge density within the sub-nanochannel significantly improves cation selectivity. Our findings provide a theoretical basis for ions transport in sub-nanochannels and an alternative strategy for design ions separation membranes.

Automated summary

Inspired by biological potassium ion channels, researchers have developed a biomimetic ion channel membrane using MXene nanosheets and EDTA molecules, which achieves efficient separation of ions. This membrane shows high ion permeability and selectivity, making it significant for sustainable water treatment, resource extraction, and energy storage.