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

A {Ru(C6H6)}-Containing Isopolymolybdate with Good Photocatalytic Activity for Oxidative Coupling of Amines, and Proton Conduction Properties

We present a nonclassical {Ru(C6H6)}-containing isopolymolybdate Cs8K2Na2H4{[(C6H6)Ru]6Mo24O86}·35H2O (1) via one-pot reaction. The crystallographic characterization of compound 1 revealed that it contains an unusual {Mo24O86} cluster together with six {Ru(C6H6)} groups, having the largest number of {Ru(C6H6)} groups within the field of {Ru(C6H6)}-containing polyoxometalates. Results showed that compound 1 displayed excellent proton conductivity (9.8 × 10-3 S cm-1) at 90 °C and 95% relative humidity. Based on the calculation result of activation energy, which was more than 0.4 eV (1.47 eV), it was determined that the proton conduction process for compound 1 was in accordance with the Vehicle mechanism. More interestingly, compound 1 was exploited as a catalyst to achieve the heterogeneous oxidative coupling of amines and realized a high yield (98.9%) toward N-benzylidenebenzylamine under ambient temperature and visible light irradiation (>400 nm) and O2 atmosphere.

Controllable Synthesis and Ultrahigh Proton Conduction of a Hydrogen-Bond Network

The functionalization of polyoxometalates with organic ligands provides a new-style strategy to accurately incorporate polyoxometalates with advanced functional organic moieties on their surfaces, the development of which has attracted increasing research interest due to the potential applications. A germanium tungstate Na2(H3O)6[{RuIV(bpy)}2{WO2(C2O4)}2(GeW11O39)2]·27H2O (bpy = 2,2'-bipyridine) with two ligands covalently modified was triumphantly synthesized, using the conventional one-pot hydrothermal method. It was systematically characterized by thermogravimetric analysis (TGA), elemental analysis, infrared (IR) spectroscopy, single-crystal X-ray diffraction, X-ray photoelectron spectroscopy (XPS), powder diffraction (PXRD), scanning electronic microscopy (SEM), and ultraviolet-visible (UV-vis) spectroscopy. The two-dimensional (2D) layered structure was established through hydrogen bonding and Na+ bridges. Impedance measurements indicate that it displays outstanding proton conduction properties, with a splendid conductivity up to 1.24 × 10-2 S·cm-1 under 353 K and 90% relative humidity (RH), owing to the rich interlayer hydrogen-bond network formed by the organic ligands ({RuC10H8N2}4+ and {WC2O4}4+), hydrated protons (H3O+), and crystal waters.

Imparting Stable and Ultrahigh Proton Conductivity to a Layered Rare Earth Hydroxide via Ion Exchange

Proton conductors are essential functional materials with a wide variety of potential applications in energy storage and conversion. In order to address the issues of low proton conductivity and poor stability in conventional proton conductors, a simple and valid ion-exchange method was proposed in this study for the introduction of stable and ultrahigh proton conductivity in layered rare earth hydroxides (LRHs). Test analyses by solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and powder X-ray diffraction revealed that the exchange of H2PO4- not only does not disrupt the layered structure of LRHs, but also creates more active proton sites and channels necessary for proton transport, thereby creating a high-performance proton conductor (LRH-H2PO4-). By utilizing this ion-exchange method, the proton conductivity of LRHs can be significantly enhanced from a low level to an ultrahigh level (>10-2 S·cm-1), while maintaining excellent long-term stability. Moreover, through methodically manipulating the guest ions and molecules housed within the interlayers of LRHs, a comprehensive explanation has been presented regarding the proficient mechanism of proton conduction in LRH-H2PO4-. As a result, this investigation presents a feasible and available approach for advancing proton conductor.

Photo-, Thermo-, Electrochromic, Erasable Inkless Printing, Ions Detection, and UV Detector Properties of Viologen Compounds Based on Homomolybdate/Keggin POMs

Three POMs-based viologen compounds with different structures were successfully constructed under solvothermal and hydrothermal conditions, [Cu(1,4-cby)2(H2O)0.5(β-Mo8O26)0.5]·C3H7NO·3H2O (1), [H2(1,4-cby)2]·(β-Mo8O26) (2) (1,4-cby·Cl = 1-(4-carboxybenzyl)-4,4'-bipyridine chloride), [H2(1,4-cbyy)2]·(SiMo12O40) (3) (1,4-cbyy·Cl = 1-(4-cyanobenzyl)-4,4'-bipyridine chloride). Compound 1 is a structure with the number "eight-like" metal-organic chain with Cu as the nodes, and compounds 2 and 3 are fascinating structures connected by hydrogen bonding interactions. More importantly, compounds 1-3 exhibit a good response to both light and electricity and the thermal response of compound 1 was also studied. The reasons for the response of compounds 1-3 to external stimuli were analyzed through methods such as UV-Vis, EPR, and XPS. In addition, the transient photocurrent response results of compounds 1-3 are the same as those obtained from kinetic calculations. Meanwhile, the coated filter paper based on compound 3 has been successfully applied in erasable inkless printing and anti-counterfeiting, the test paper of 3 can also detect metal ions, and the films based on compounds 1-3 are a flexible and portable ultraviolet (UV) detector.