Ultraselective Monovalent Metal Ion Conduction in a Three-Dimensional Sub-1 nm Nanofluidic Device Constructed by Metal–Organic Frameworks

Abstract

Construction of nanofluidic devices with an ultimate ion selectivity analogue to biological ion channels has been of great interest for their versatile applications in energy harvesting and conversion, mineral extraction, and ion separation. Herein, we report a three-dimensional (3D) sub-1 nm nanofluidic device to achieve high monovalent metal ion selectivity and conductivity. The 3D nanofluidic channel is constructed by assembly of a carboxyl-functionalized metal–organic framework (MOF, UiO-66-COOH) crystals with subnanometer pores into an ethanediamine-functionalized polymer nanochannel via a nanoconfined interfacial growth method. The 3D UiO-66-COOH nanofluidic channel achieves an ultrahigh K+/Mg2+ selectivity up to 1554.9, and the corresponding K+ conductivity is one to three orders of magnitude higher than that in bulk. Drift-diffusion experiments of the nanofluidic channel further reveal an ultrahigh charge selectivity (K+/Cl–) up to 112.1, as verified by the high K/Cl content ratio in UiO-66-COOH. The high metal ion selectivity is attributed to the size-exclusion, charge selectivity, and ion binding of the negatively charged MOF channels. This work will inspire the design of diverse MOF-based nanofluidic devices for ultimate ion separation and energy conversion.

Super-assembly of freestanding graphene oxide-aramid fiber membrane with T-mode subnanochannels for sensitive ion transport

“…S23†), which suppresses the transmission of divalent metal ions. 10,11 The pH-dependent ion transport can also verify this point (Fig. 4g–i and Fig.…”

“…4–9 Thus, it is desirable to develop membrane-based nanofluidic devices to achieve efficient and selective ion transport. Solid-state nanochannels with a confined space that selectively transport ions or molecules at the nano- or sub-nanometre (sub-nm) scale have attracted growing interest over the past few decades, which are widely applied for ion sieving 10,11 and energy conversion. 12,13…”

Lithium Extraction by Emerging Metal–Organic Framework‐Based Membranes

“…Recently, they further grew UiO‐66‐COOH in PET single‐nanochannel membrane to investigate the ion transport property. [ 62 ] As the decrease of COOH density comparing to UiO‐66‐(COOH) 2 , more space will be there in the window of the framework for ion transport, resulting in higher ion conductivity of the MOFC membrane and lower mono‐/di‐valent ion selectivity (≈200 for Li + /Mg 2+ ). This result also indicated the influence on ion selectivity of MOF by the charge density.…”

Angstrom-scale ion channels towards single-ion selectivity

“…6B). The confined growth methods include in situ growth, [119][120][121][122] interfacial growth, 123 and seeding facilitated interfacial growth. 124,125 Polycrystalline UiO-66 membranes were fabricated onto the surface of alumina hollow fibers by in-situ growth 122 (Fig.…”