Ionothermal Synthesis of Five Keggin-Type Polyoxometalate-Based Metal–Organic Frameworks

Abstract

Five unique Keggin-type polyoxometalate (POM)-based metal−organic frameworks (POMFs), namely= 1,4-bis((1H-1,2,4-triazol-1-yl)methyl)-benzene, have been synthesized under ionothermal conditions. According to single-crystal data, 1 exhibits a novel mechanically interlocked molecular architecture (MIMA) constructed by two-dimensional (2D) interpenetrating polyrotaxane layers with unique cyclophanes (tetra-cationic viologen macrocycle cyclobis-(paraquat-p-phenylene) (CBPQT 4+ system)), resulting in an H-bonded 3D supermolecule, and is the first synthesis of selfassembled cyclophane-PMOFs under ionothermal conditions. 2 shows a novel 2D three-fold interpenetrating polyrotaxane host and guest network. 1 and 2 are presented as the first MIMA polyrotaxane structures to have been synthesized under ionothermal conditions. Electrochemical impedance spectroscopy (EIS) reveals that 2, 4, and 5 show high proton conductivity owing to their unique structural properties. Solid-state diffuse reflection UV−vis-NIR measurements show the title compounds are potentially semiconductor materials. Photocatalytic investigations indicate that 1−5 possess high and stable photocatalytic H 2 evolution and rhodamine B (RhB) degradation under visible-light irradiation.

Tunable Metal Oxide Frameworks via Coordination Assembly of Preyssler-Type Molecular Clusters

“…It is perhaps curious that Zn-bridged frameworks exhibit roughly the same conductivity as those bridged with Mn, Co, Ni, or Cu, although similar trends have been observed for Zn- compared to Co- or Cu-based MOFs . This result may suggest that conductivity in the Zn-bridged frameworks is ionic rather than electronic, as POMs and POM-based coordination polymers have been shown to be good proton conductors under some conditions. − …”

Hourglass-Type Polyoxometalate-Based Crystalline Material as an Efficient Proton-Conducting Solid Electrolyte

“…Hitherto, the proton conductivity of CUST-571 reached 4.54 × 10 –3 S cm –1 at 85 °C and 98% RH, which is much higher than those of most of the POM-based hybrid proton-conducting composites (Table S4). , …”

Polyoxometalates: Tailoring metal oxides in molecular dimension toward energy applications

“…265 The Keggin-type Mo 12 O 40 polyoxomolybdatesbased metal-organic frameworks have been synthesized, and efficient H 2 evolution under light irradiation and effective rhodamine degradation have been observed. 266 (NH 4 ) 3 H 4 [PMo 11 VO 40 ]Á3.5H 2 O facilitates the formation of Ni-S hollow microspheres, resulting in a 77 mV overpotential at 10 mA/cm 2 current density for hydrogen evolution attributed to the improved surface area and electrical conductivity of the catalyst. 267 The Andersontype NiMo 6 O 24 functions as efficient electrocatalyst for hydrogen fuel production, since the polyoxometalate improves the H + transfer and the H abstraction.…”

“…By incorporating H 3 PMo 12 O 40 polyoxometalate and gold nanoparticles on WO 3 substrates, undesirable formation process of the recombination centers can be retarded . The Keggin‐type Mo 12 O 40 polyoxomolybdates‐based metal‐organic frameworks have been synthesized, and efficient H 2 evolution under light irradiation and effective rhodamine degradation have been observed . (NH 4 ) 3 H 4 [PMo 11 VO 40 ]·3.5H 2 O facilitates the formation of Ni‐S hollow microspheres, resulting in a 77 mV overpotential at 10 mA/cm 2 current density for hydrogen evolution attributed to the improved surface area and electrical conductivity of the catalyst .…”