Keeping Superprotonic Conductivity over a Wide Temperature Region via Sulfate Hopping Sites‐Decorated Zirconium‐Oxo Clusters

Abstract

Nevertheless, perfluorinated polymers usually involve complex synthesis process. Besides, they are amorphous polymers without clear structures, which make it challenging to uncover their proton transport mechanism for directionally improving the proton conducting performances. [4] Recently, crystalline porous materials such as metal-organic frameworks (MOFs) and metal-oxo clusters have been extensively investigated in the pursuit of new proton conductors. [5] In particular, porous MOFs have attracted great attention because of their diverse structures and high porosity. Besides, their proton conducting performances can be effectively improved through structural functionalization, such as decorating functionalized groups (e.g., SO 3 H, COOH, and PO 3 H 2 ) on the linkers or adding proton carriers (e.g., imidazole and sulfuric acid) into the porous channels. [6] Nevertheless, many porous MOFs are sensitive to water and easily to lose guest/ water molecules, especially under high temperature, which make a great challenge for their application under these conditions. [7] Compared with MOFs, crystalline metal-oxo clusters, especially those constructed by high valence metal ions and O-contained ligands (e.g., SO 4 2− and PO 4 2−) usually show more stable in aqueous media. [8] In addition, their hydrophilic O-rich surface can function as proton hopping sites and binding sites Metal-oxo clusters have emerged as advanced proton conductors with welldefined and tunable structures. Nevertheless, the exploitation of metal-oxo clusters with high and stable proton conductivity over a relatively wide temperature range still remains a great challenge. Herein, three sulfate groups decorated zirconium-oxo clusters (Zr 6 , Zr 18 , and Zr 70 ) as proton conductors are reported, which exhibit ultrahigh bulk proton conductivities of 1.71 × 10 −1 , 2.01 × 10 −2 , and 3.73 × 10 −2 S cm −1 under 70 °C and 98% relative humidity (RH), respectively. Remarkably, Zr 6 and Zr 70 with multiple sulfate groups as proton hopping sites show ultralow activation energies of 0.22 and 0.18 eV, respectively, and stable bulk conductivities of >10 −2 S cm −1 between 30 and 70 °C at 98% RH. Moreover, a time-dependent proton conductivity test reveals that the best performing Zr 6 can maintain high proton conductivity up to 15 h with negligible loss at 70 °C and 98% RH, representing one of the best crystalline cluster-based proton conducting materials.

Controlled Assembly of a Dawson-like Antimoniotungstate-Supported Trefoil-type Trimer with Good Proton Conductivity Performance

“…With different humidity varying from 55 to 80%, the conductivity (σ) of compound 1 gradually climbed up from 3.28 × 10 –5 to 4.50 × 10 –3 S cm –1 (Figure a,c), demonstrating a dramatic increase with relative humidity increasing, which may be due to the fact that more mobile proton transfer sites are provided by water molecules . On the other hand, the results are consistent with the water absorption isotherm, and the absorption of a large number of water molecules by compound 1 at high humidity to form hydrogen bonds with a large number of surface oxygen atoms in the interlayer also accelerates the proton transfer. − In addition, as another crucial influence factor, temperature-dependent proton conductivity measurements also were probed by using the same sample 1 . As shown in Figure b, as the temperature rose from 30 to 75 °C under 80% RH, the conductivity increased continuously to 3.07 × 10 –2 S cm –1 , which was attributed to the acceleration of proton transfer with the temperature rising up (Figure b) .…”

Ce-Mediated Molecular Tailoring on an Unprecedented Gigantic Polyoxometalate {Mo132} into Half-Closed Product {Ce11Mo96} for Achieving High Proton Conduction

“…5d and 5e), suggesting less temperature dependent proton conductivity, which is a rare example of metal-oxo clusters-based proton conductors that keep high and stable proton conductivity over a relatively wide temperature region. [36][37] The maximum proton conductivity of 2 close to the order of 10 − 1 S cm -1 features one of the representative POMs-based crystalline proton conductors [38][39][40][41] (Table S10) and is comparable to those of well-known crystalline metal-organic (e.g. MOF-808-4SA-150 [42] , BUT-8-(Cr)A [43] ,…”

Construction of zirconium/hafnium-oxo clusters based on a new protection-calix[8]arene

“…[7][8][9] However, as ZrOCs and HfOCs prefer to retain their inorganic cores and have little ligand exchange, cluster collapse may often occur, and thus, ZrOCs (HfOCs) with good stability must urgently be developed. 10,11 To create stable ZrOCs (HfOCs), it is particularly important to consider protective ligands. Widely recognized candidates in this regard are carboxylic acids, carboxylates and inorganic anions.…”

“…7–9 However, as ZrOCs and HfOCs prefer to retain their inorganic cores and have little ligand exchange, cluster collapse may often occur, and thus, ZrOCs (HfOCs) with good stability must urgently be developed. 10,11…”