Aligned amino-functionalized γ-cyclodextrin nanofiltration membrane via customized interfacial polymerization for precise Li+/Mg2+ separation

Abstract

Membrane consisting of high-throughput aligned ion channels has been pursued for precise Li⁺/Mg²⁺ separation. Herein, an aligned amino-functionalized γ-cyclodextrin nanofiltration membrane was fabricated via a customized interfacial polymerization technique, where the orientation of cyclodextrin ion channels was elaborately tailored by controlling the reaction conditions. The as-fabricated membrane featured ultra-thin selective layer of ∼ 26 nm, average pore size of ∼ 0.72 nm, and ultra-stable positive surface charges. In particular, the aligned intrinsic cyclodextrin cavities in the membrane offered vertical shortcuts for preferential Li⁺ transport. Taking advantage of these, superior membrane permselectivity was achieved with the water permeance of 6.5 L·m⁻²·h⁻¹·bar⁻¹ and the Li⁺/Mg²⁺ separation factor up to 22.5, highlighting the great potentials in lithium extraction and other ion separations. Given its simplicity and generality, this customized interfacial polymerization strategy holds great promise for manipulating aligned transport channels in thin film composite membranes, thereby enhancing their performance in a wide range of applications including, but not limited to, desalination, water purification, resource extraction, and energy conversion.