The First Demonstration of the Gyroid in a Polyoxometalate‐Based Open Framework with High Proton Conductivity

Abstract

The fabrication of extended open frameworks with crystalline ordering on the atomic level by following peculiar mathematical geometry (e.g. Möbius band, Klein bottle, periodic minimal surfaces, etc.) is challenging, but extremely beneficial for discovering non-trivial structure-dependent properties. In light of this, we herein report the first polyoxometalate-based open framework (POM-OF) that definitely lies on the gyroid (G)-minimal surface, which was constructed by a rare pair of chiral POM enantiomers and zinc ions. Due to the presence of the proton carriers (i.e., water, Na(+) , [(Bu)4 N](+) , etc.) in the resultant gyroidal channels, with pore dimensions on the order of the quasi-mesoporous scale, this compound shows a high proton conductivity of 1.04×10(-2) S cm(-1) at a relative humidity of 75 % (80 °C), and also exhibits enormous potential in the application of electrochemical catalysis.

Self-Assembly of Giant Mo240 Hollow Opening Dodecahedra

“…As shown in Figure c, the proton conductivity increases with the increasing temperature. This should be attributed to possible promotion of H 3 O + ion formation (from H 2 O and H + ) at elevated temperatures and thus accelerate the proton transition within the channels. ,, At 80 °C and 98% RH, the proton conductivity reaches 1.03 × 10 –1 S cm –1 , which is the highest among the reported crystalline, POM-based proton conductors (Table S4) ,− and comparable to those of the high-performing metal–organic (MOF) and covalent–organic (COF) frameworks. ,,− Indeed, there are only a few MOFs and COFs, including BUT-8­(Cr)­A, PCMOF2 1/2 (Tz or Pz), IM-UiO-66-AS, and H 3 PO 4 @COFs, with proton conductivities on the order of 10 –1 S cm –1 under analogous conditions (Table S4). To investigate the conductivity stability of 1 , the proton conductivity was monitored for 24 h at 80 °C and 98% RH, and negligible change was noted (Figure S22).…”

“…At 25 °C and 98% RH, the proton conductivity of 1 reaches a maximum of 3.33 × 10 –2 S cm –1 , which is significantly higher than most known POM-based crystalline proton conductors under analogous conditions (Table S4). ,− The highly humidity-dependent proton conductivity implies that the water molecules play a significant role in conduction and that protons migrate primarily inside and outside of pores and channels in 1 . ,, As demonstrated by the room-temperature H 2 O vapor sorption measurement (Figure S18), 1 has an outstanding water uptake capacity under high humidities. This may facilitate the construction of hydrogen bond networks that can act as proton transport pathways within the channels of 1 , thus leading to outstanding conductivity. ,, …”

“…Furthermore, cage 1 shows high stability in solution and can be visualized by scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) imaging. In addition, the bulk conductivities of 1·g reached 3.33 × 10 –2 S cm –1 at 25 °C and 98% relative humidity (RH) and 1.03 × 10 –1 S cm –1 at 80 °C and 98% RH, respectively, representing the highest among the reported POM-based crystalline proton conductors under the analogous conditions. ,− …”

Control of Proton‐Conductive Behavior with Nanoenvironment within Metal–Organic Materials

“…In 11− enantiomers and zinc ions. [78] This compound reveals a high proton conductivity of 1.04 × 10 −2 S cm −1 at 75% RH (80 °C) probably because of the large number of proton carriers (like water) and hydrophilic guests in the relatively large-sized POM-based 3D framework.…”

A Hexanuclear Cadmium Metal–Organic Framework Exhibiting Dual Mechanisms to Trigger a Fluorescence‐Quenching Response toward Iron(III) Ions

“…Metal–organic frameworks (MOFs) are constructed through the ordered assembly of organic ligands and metal ions or clusters . As a new class of inorganic–organic hybrid crystalline materials with tailorable topologies, MOFs have promising applications in many fields such as gas storage and separation, catalysis, drug delivery, proton conduction, and chemical sensing . Recently, increasing attention has been paid to the fluorescent responses of MOFs toward guest species such as organic molecules and metal ions, and this behavior has encouraged the development of new kinds of fluorescent materials as well as new spectral analysis methods.…”