Silica-based functionalized glass micropore enabling K+ / Mg2+ sieving through the synergistic effect of crown ethers and EDTA

Development of a K + / Mg 2+ device : Silica nanowires were co‑functionalized with CB18C6 and EDTA to fabricate a CB18C6&EDTA/SiNWs/GMP ion selective device. • Improvement in selectivity : The synergistic effect of CB18C6 and EDTA greatly enhances K⁺/Mg²⁺ selectivity up to 331.16 compared with single ligand device. • K + Preferred Conductance : The fabricated device displays preferential K⁺ conductance in KCl and MgCl₂ mixed solution against varying Mg²⁺ concentrations. • Device Stability : The device keeps stable K⁺/Mg²⁺ selectivity under diverse ion concentrations and after long term storage. • Practical applicability : The K⁺/Mg²⁺ selectivity of the device is well maintained under simulated human body pH conditions. Biomimetic ion channels have attracted extensive attention for ion separation applications owing to their nanoscale or even sub-nanoscale confined structures, as well as the ease of surface functionalization. K + and Mg 2+ are indispensable biological ions involved in a wide range of physiological processes necessary for normal life activities. Due to the similar hydrated ionic radius and high water solubility of K + and Mg 2+ , it remains difficult to separate these ions using conventional materials. To address this challenge, herein we report a functionalized glass micropore (GMP) in which silica nanowires (SiNWs) were introduced into the GMP to serve as a supporting framework, followed by functionalization of the SiNWs with 4′-Carboxybenzo-18-crown-6 (CB18C6) and ethylenediaminetetraacetic acid (EDTA). The constructed functionalized GMP takes advantage of the excellent size matching between the cavity of CB18C6 and the radius of K + , together with the chelation effect of EDTA toward Mg 2+ . Through the synergistic effect of these two functional molecules, highly efficient ion sieving was achieved. Under the same solution volume conditions, the optimal selectivity was obtained when the mass ratio of CB18C6 to EDTA was 4:1, with the selectivities of K + / Na + , K + / Mg 2+ , and K + / Ca 2+ reaching 1.51, 331.16, and 98.16, respectively. The proposed functionalised GMP recognises K + based on the properties of the functional molecules, exhibiting excellent ion sieving performance between target ions and competing ions. This work provides a new research strategy for precise K + / Mg 2+ separation technology. Download: Download high-res image (134KB) Download: Download full-size image Schematic illustration of K +  / Mg 2+  ion sieving in a functionalized GMP based on SiNWs, achieved through the synergistic effect of CB18C6 and EDTA. The diagrams are not drawn to scale.