Three Proton‐Conductors Based on Keggin‐Type Polyoxometalates Well‐Arranged in the Networks of Dinuclear‐Cu(II)‐Mixed‐Organic‐Ligand Clusters

Abstract

Three proton‐conductors, [Cu(5‐H2L)(IN)(H2O)]2H2[SiW12O40] ⋅ 2CH3CN ⋅ 2.5H2O (1), [Cu(4‐HL)(HIN)(H2O)]2H2[SiW12O40] ⋅ 7H2O (2) and [Cu(4‐HL)(HIN)(CH3CN)]2[HIN]2H4[PMo12O40]2 ⋅ 2CH3CN ⋅ 12H2O (3) (where 5‐H2L/4‐H2L is 5,5’/4,4’‐bis(hydroxymethyl)‐2,2’‐bipyridine and HIN is isonicotinic acid), were synthesized at room temperature. Interestingly, three dinuclear‐Cu(II)‐mixed‐organic‐ligand clusters, [Cu(5‐H2L)(IN)(H2O)]22+ cluster for 1, [Cu(4‐HL)(HIN)(H2O)]22+ for 2 and [Cu(4‐HL)(HIN)(CH3CN)]22+ for 3, are in situ synthesized under the coexistence of Keggin‐type polyoxometalates. More interestingly, in 1–3, the global Keggin‐type anions are well‐arranged in the hydrogen‐bonding networks of double‐Cu(II)‐mixed‐organic‐ligand clusters to give different spatial arrangement patterns. The [SiW12O40]4− anions in 1 display two dimensional layer pattern. The [SiW12O40]4− anions in 2 act as single bidentate O,O bridge ligands. The [PMo12O40]3− anions in 3 form the pair pattern. The AC impedance measurement results reveal 3 gives a high conductivity value over 10−3∼10−2 S ⋅ cm−1 in a wide temperature range from 25 to 100 °C under a wide relative humidity range from 35 to 98 %, while 1 and 2 give a middle conductivity value over 10−5∼10−4 S ⋅ cm−1 under the same conditions.

Space-Confined Nucleation of Semimetal-Oxo Clusters within a [H7P8W48O184]33– Macrocycle: Synthesis, Structure, and Enhanced Proton Conductivity

“…As shown in Figure a,b, conductivity depends closely on the specific RH at 35 °C. The value increased from 4.8 × 10 –4 (55% RH) to 1.2 × 10 –3 S cm –1 (70% RH), which is superior to the conductivity of most reported proton-conductive POMs under similar conditions. − With increasing temperature, the conductivity increased rapidly and achieved 1.2 × 10 –2 S cm –1 as the maximum at 85 °C (Figure c,d), which is among the highest proton conductivities yet found in POM-based materials under similar operating conditions (Table S4), holding great prospects as solid electrolytes in proton-exchange membrane (PEM) fuel cells. ,,,− The research data has shown that the proton-conductive performance of DMA-KNaLi-As 10 is heavily affected by a combined impact of temperature and RH. Clearly, the proton transport in DMA-KNaLi-As 10 might be markedly enhanced under hot and humid environments.…”