Organic Hybrid Antimoniotungstate Layered Ionic Crystal: Synthesis, Structure, and Interlayer-Confined Proton Conduction

Abstract

A synchronous crystal- and microstructure-dependent strategy was implemented to synthesize the organic hybrid antimoniotungstate layered ionic crystal Na5.5H6.5[(SbW9O33)2{WO2(OH)}2{WO2}­RuC7H3NO4]·36H2O, and the layered structure was constructed through the Na+ bridged sheet and the hydrogen-bonded layers. It displayed an effective proton conductivity of 2.97 × 10–2 S cm–1 at 348 K and 75% RH, owing to the complete interlayer confined hydrogen-bond network formed by the hydrogens of interlayer crystal waters, organic ligands ({RuC7H3NO4}2+, {C7H3NO4} is formed by the hydrolysis of pyridine 2,5-dicarboxylic acid (C7H5NO4)), and acidic protons (H+), along with the interlayer domain as a transport channel. Furthermore, the hydrogen-bond network originating from interlayer organic ligands and acidic protons was more stable at a higher temperature of 423 K, preserving a high conductivity of 1.99 × 10–2 S cm–1.

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

“…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) . Although ordinary in comparison with the proton-conducting materials such as MOF, COF, HOF, etc., it is superior to typical proton-conducting materials in POMs ,− (Table S7). At last, the activation energy ( E a ) was evaluated by the Arrhenius equation [σ T = σ 0 exp(− E a / k b T )], and calculations showed that E a at 80% RH was estimated to be 0.22 eV (Figure d), indicating that the Grotthuss mechanism is dominant during the process of proton conduction, given that E a is in the range from 0.1 to 0.4 eV .…”

A Hexameric Ruthenium(III)-Containing Tungstoantimonate with Good Proton Conductivity Performance

“…In comparison, the conductivity of 1 -dehyd is 40-fold that of compound 1 at 55% RH. This result concludes that the large number of water molecules within complex 1 is beneficial for promoting the proton conduction process . The infrared spectra of the initial compound 1 and its dehydrated form, 1 -dehyd, were examined before and after proton conduction testing (Figure S6).…”

“…In addition, most of the related studies focused on POMs built from 3d block transition metals and lanthanide elements, while rare studies were conducted on 4d block transition metal-based POMs in this field. For example, organo-ruthenium supported antimoniotungstate [Sb 2 W 20 O 70 (RuC 10 H 14 ) 2 ] 10– was attained in 2009; bis­[tetraruthenium­(IV)]-containing polyoxometalates of [{Ru IV 4 O 6 (H 2 O) 9 } 2 Sb 2 W 20 O 68 (OH) 2 ] 4– was reported in 2012, and Niu group reported an organic hybrid antimoniotungstate layered ionic crystal Na 5.5 H 6.5 [(SbW 9 O 33 ) 2 {WO 2 (OH)} 2 {WO 2 }­RuC 7 H 3 NO 4 ]·36H 2 O with high proton conductivity in 2023 …”

A wheel-shaped Zr-substituted phosphotungstate [{Zr(C2O4)2}3 (PO4)(P6W39O150)]39− with tunable proton conduction properties

“…36 Besides, our group reported a high-conductivity POM Na 5.5 H 6.5 [(SbW 9 O 33 ) 2 {WO 2 (OH)} 2 {WO 2 }RuC 7 H 3 N O 4 ]·36H 2 O with σ = 2.97 × 10 −2 S cm −1 (75% RH, 348 K) in 2023. 37 Compared with these POM-based proton conductive materials (Table S3, ESI‡), ZrSPs as proton conduction materials are rare, and the proton conductivity of 1 is superior to that of most POM-based proton conductive materials.…”