Efficient Gating of Ion Transport in Three‐Dimensional Metal–Organic Framework Sub‐Nanochannels with Confined Light‐Responsive Azobenzene Molecules

Abstract

1D nanochannels modified with responsive molecules are fabricated to replicate gating functionalities of biological ion channels, but gating effects are usually weak because small molecular gates cannot efficiently block the large channels in the closed states. Now, 3D metal–organic framework (MOF) sub‐nanochannels (SNCs) confined with azobenzene (AZO) molecules achieve efficient light‐gating functionalities. The 3D MOFSNCs consisting of a MOF UiO66 with ca. 9–12 Å cavities connected by ca. 6 Å triangular windows work as angstrom‐scale ion channels, while confined AZO within the MOF cavities function as light‐driven molecular gates to efficiently regulate the ion flux. The AZO‐MOFSNCs show good cyclic gating performance and high on–off ratios up to 17.8, an order of magnitude higher than ratios observed in conventional 1D AZO‐modified nanochannels (1.3–1.5). This work provides a strategy to develop highly efficient switchable ion channels based on 3D porous MOFs and small responsive molecules.

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.…”

Photoresponsive Solid Nanochannels Membranes: Design and Applications

“…Most recently, Wang et al constructed the photoresponsive sub-nanochannels by confining Azo molecules into the MOF UiO-66. [44] In the photoresponsive UiO-66-Azo channels, trans-Azo was transformed into cis-Azo under UV light, resulting in a smaller MOF cavity, blocked MOF pores and the ionic transport switching from ON to OFF (Figure 2e). [44] Except for ionic gating, an Azo-DNA modified nanochannel can also be used to control the transport of adenosine triphosphate (ATP) (Figure 2f).…”

Progress in Multifunctional Metal–Organic Frameworks/Polymer Hybrid Membranes

“…In order to mimic biological rectifying ion channels, Wang and co-workers developed a series of PET-MOF sub-nanochannels, realized ultrahigh selective F À conductivity, [64] rapid monovalent cations conduction [65] and photo-gating of ion transport. [66] Unlike the previously reported physical doped or covalent immobilized MOF-polymer membranes, their subnanochannels were prepared by filling MOFs into nanometersized bullet-shaped poly(ethylene terephthalate) (PET) membranes. The bullet-shaped single-nanochannel PET membranes act as supports, the MOFs with angstrom-sized pore windows and specific binding sites act as ion channels to ensure highly selective and rapid ions transportation.…”

“…In order to mimic biological rectifying ion channels, Wang and co‐workers developed a series of PET‐MOF sub‐nanochannels, realized ultrahigh selective F − conductivity, [64] rapid monovalent cations conduction [65] and photo‐gating of ion transport [66] . Unlike the previously reported physical doped or covalent immobilized MOF‐polymer membranes, their sub‐nanochannels were prepared by filling MOFs into nanometer‐sized bullet‐shaped poly(ethylene terephthalate) (PET) membranes.…”