Unusually Flexible Indium(III) Metal–Organic Polyhedra Materials for Detecting Trace Amounts of Water in Organic Solvents and High Proton Conductivity

Abstract

Humidity-induced single-crystal transformation was observed in the indium metal-organic polyhedra [In(TCPB)]·2HO (In1), where HTCPB is 1,3,5-tri(4-carboxyphenoxy)benzene. When the humidity is above 58% relative humidity (RH) at room temperature, the neutral compound In1 could be successfully converted into the positively charged compound In1-H along with the color change from yellow to deep red, which also undergoes a reversible transformation into In1 driven by thermal dehydration. Notably, the color of In1 takes only 5 min to change under 58% RH at room temperature, which is much quicker than common desiccant bluestone. As the water content is increased from 0.0% to 0.2% in acetonitrile solvent, compound In1 exhibits rapid detection of trace amounts of water through turn-off luminescence sensing mechanism with a low detection limit of 2.95 × 10%. Because of the formation of extensive hydrogen-bonding network between the metal-organic polyhedra (MOPs) and surrounding guest OH ions, compound In1-H, along with isostructural Ga1-H, displays excellent proton conductivity up to 2.84 × 10 and 2.26 × 10 S cm at 298 K and 98% RH, respectively. Furthermore, the activation energies are found to be 0.28 eV for In1-H and 0.34 eV for Ga1-H. This method of incorporation of OH ions to obtain high proton conductivity MOPs with low activation energy demonstrates the advantage of OH ion conduction in the solid-state materials.

Chemical Sensors for Water Detection in Organic Solvents and their Applications

“…Displacement of metal from complex or coordination with metal leads to water detection using the metal complex as a chemical sensor. The metal complex of transition and lanthanides ions, [50,51] metal‐based luminescent and phosphorescent nanomaterials, [18a] metal‐organic frameworks (MOFs) [52] and metal‐organic polyhedra (MOPs) [53] are mainly used for moisture detection.…”

“…It shows greater sensitivity to water concentration with LOD 0.05 % v/v. [53] ). (B) Color change image of Eu-MOF in the presence of the different amounts of water contents (0.05-10 % v/v) in DMF observed under a UV lamp.…”

An Indium‐Seamed Hexameric Metal–Organic Cage as an Example of a Hexameric Pyrogallol[4]arene Capsule Conjoined Exclusively by Trivalent Metal Ions

“…For instance, analogues of the current In 3+ ‐seamed MONCs doped with 111 In 3+ ( t 1/2 =2.68 days) appear particularly compelling owing to potential applications in molecular imaging . Certain indium‐based polyhedral complexes have exhibited remarkable proton conductivities up to 2.84×10 −4 S cm −1 and could serve as sensors to detect trace amounts of water …”

The crystal structure of dimethylammonium catena-[di(μ-aqua)-bis(μ9-benzene-1,3,5-tricarboxylato)pentalithium], C20H16Li5NO13

“…Metal-organic frameworks (MOFs) are porous materials composed of metal ions/clusters and organic units, which have the characteristics of porosity, high specific surface area and are easy to modify. MOFs and CPs are widely used in gas storage and separation [4], fluorescent responses [5], proton conductivity [6], membrane separation [7,8], environmental pollution control [9,10] and energy conversion [11,12]. However, most of the MOFs are constructed from the transition metals or rare earth, and the alkali-metal-based MOFs are rare examples, particularly the lithium-based MOFs [13,14].…”