Photoswitchable Nanoporous Metal–Organic Framework Monolayer Film for Light-Gated Ion Nanochannel

Abstract

Two-dimensional metal−organic framework (MOF) monolayer films, which can be considered as large-area, periodically ordered thin films with atom-or single-unit thickness, have attracted extensive attention due to their special properties and wide range of potential applications. However, the preparation of MOF monolayer films is still a great challenge, and the introduction of functional groups into MOF monolayer films is seldom reported. Here, we report the first centimeterscale, photo-switchable, free-standing MOF monolayer film formed by self-assembly of poly(methyl methacrylate-co-acrylamidoazobenzene)-coated MOF nanoparticles at the water−air interface. This self-assembled MOF monolayer film is extremely thin (∼220 or 50 nm) and has a high MOF loading (85 wt %), while exhibiting remarkable reversible photoswitching properties under alternating exposure to 365 nm UV and white light. Inspired by this, a light-gated ion nanochannel device is fabricated, which enables reversible ″OFF−ON″ changes of the ionic flux and has promising applications in the field of photoelectric conversion. This provides a modular route to design large-area, free-standing functional MOF monolayer films.

Self‐Assembled Nanoporous Metal–Organic Framework Monolayer Film for Osmotic Energy Harvesting

“…The SAMM of UiO-66-NH 2 -P(MMA 0.99 -co-VIM 0.01 ) was fabricated through evaporation-induced interfacial assembly at the water−air interface, which was named SAMM-2. [50][51][52] First, MOF NPs were dispersed in toluene (50 mg mL −1 ); then, 10 μL of the suspension of the NPs was gently dropped onto a water surface in a 35 mm diameter Petri dish. The suspension immediately spread and formed a monolayer film (Figure 1e inset, Scheme 1b).…”

“…In addition, the functional modification of the SAMM film is very likely to destroy its close‐packed structure, resulting in large defects in the thin film. [ 52 ] Therefore, it is still a great challenge to prepare functionalized SAMM films and advance their practical applications under the premise of ensuring the integrity of the SAMM films.…”

“…[50] This SAMM film maintains the properties of MOF materials and exhibits a short mass transfer path because of its ultrathin thickness; thus, it circumvents the "permeability−selectivity" trade-off and shows promising potential for osmotic energy harvesting. Although several SAMM films have been reported, [50][51][52] these SAMM films are too fragile for further processing, and the lack of functional groups on the films hinders their practical applications. In addition, the functional modification of the SAMM film is very likely to destroy its close-packed structure, resulting in large defects in the thin film.…”

Bio-inspired High-Performance Artificial Ion Pump Mediated by Subnanoscale Dehydration Hydration Effects

“…Benefiting from the regular octahedral cage structures and angstrom-size confinement space of UiO-66 crystals, the collected ions in the cavity were partially dehydrated and trapped in the cages at high concentrations, which limited the ion leakage and contributed to keeping the stability of the ion gradient. 23,24 In view of the above design strategy, first, the ionic transport behavior in the MOF was investigated by comparing the ion mobility in UiO-66-filled PET channels (PET-UiO66) and PET channels. A molecular dynamics model was constructed to simulate the ion dehydration and hydration behavior in UiO-66 cages at different concentrations to reveal the subnanoconfinement effects in ion diffusion processes.…”

“…In this research, the ion-selective nanovalves at both ends were constructed by polystyrene- b -poly­(4-vinylpyridine) (PS- b -PVP) and polystyrene- b -poly­(acrylic acid) (PS- b -PAA) block copolymer (BCP) porous membranes, which provided high ionic flux and abundant surface charges by regulating the functional group distribution. , The ion storage cavity was constructed by zirconium-based UiO-66 metal–organic framework-filled polyethylene terephthalate (PET) columnar microchannels. Benefiting from the regular octahedral cage structures and angstrom-size confinement space of UiO-66 crystals, the collected ions in the cavity were partially dehydrated and trapped in the cages at high concentrations, which limited the ion leakage and contributed to keeping the stability of the ion gradient. , …”