Preparation of an aqueous zinc ion rGH/V2O5 photorechargeable supercapacitor.

A photorechargeable supercapacitor was constructed using vanadium pentoxide (V2O5), reduced graphene oxide hydrogel (rGH), and zinc trifluoromethanesulfonate (Zn(CF3SO3)2) as the photoanode, cathode, and electrolyte, respectively. The phase composition, microstructure, chemical structure, light absorption, and specific surface area of the synthesized products and the electrochemical performance of the rGH/V2O5 supercapacitor were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV-Vis spectroscopy, the Brunauer-Emmett-Teller (BET) method, and an electrochemical workstation, respectively. The results show that the device has a specific capacity of 164 F g-1 at 0.5 A g-1 under illumination with 95 mW cm-2 light intensity, which is 20.5% higher than that under normal electrical charging. The supercapacitor has a 75% capacity retention rate and 100% coulombic efficiency, respectively, after 10 000 testing cycles under photoelectric synergistic charging and discharging. The as-constructed rGH/V2O5 photorechargeable supercapacitor exhibits promising application potential in electric vehicles and wearable electronics.

Detection of host-guest interactions in clathrates of heterocyclic molecules adsorbed in a porous MOF with Cu2 cluster nodes via vibration spectra and magnetic properties.

A three-dimensional NbO-type MOF with the formula Cu2(EBTC)(H2O)2·[G] (1) (EBTC(4-) = 1,1'-ethynebenzene-3,3',5,5'-tetracarboxylate; G = guest molecules and represent DMF, DMSO and H2O) was synthesized using a solvothermal method. The sufficient cavity space in 1 can be used to encapsulate the heterocyclic compounds benzopyrrole (C8H7N), benzofuran (C8H6O) and benzothiophene (C8H6S). The guest-free framework (2) was obtained by heating methanol-exchanged 1 at 130 °C under vacuum. The clathrates [Cu2(EBTC)(H2O)2·1.6C8H7N]∞ (3), [Cu2(EBTC)(H2O)2·2.5C8H6O]∞ (4) and [Cu2(EBTC)(H2O)2·2C8H6S]∞ (5) were prepared by soaking 2 in C8H7N, C8H6O and C8H6S at 55 °C for 48 h, respectively. 1-5 showed quite similar PXRD patterns, indicating that they have the same framework structure. The IR and Raman spectra and the variable-temperature magnetic susceptibilities were comparatively studied for 1-5; the results disclosed the existence of weakly intermolecular interactions between the -C≡C- in the organic linkers and guest molecules, whereas an almost complete absence of intermolecular interactions between the paddle-wheel-type dinuclear Cu2 units and large guest molecules owing to steric hindrance. This study suggests the possibility of these rather useful MOF materials in the removal of organosulfur or organonitrogen compounds that are widely known contaminants in petroleum and fuels via their rationally designed organic linkers.

Comparative study of structures, thermal stabilities and dielectric properties for a ferroelectric MOF [Sr(µ-BDC)(DMF)]∞ with its solvent-free framework.

A ferroelectric MOF with a formula [Sr(µ-BDC)(DMF)]∞ (1) was transformed into [Sr(µ-BDC)(CH2Cl2)x]∞ (2) using a solvent exchange approach, where DMF = N,N-dimethylformamide and BDC(2-) = benzene-1,4-dicarboxylate. The lattice solvents, CH2Cl2 molecules, in 2 were removed by heating to give the solvent-free metal-organic framework [Sr(µ-BDC)]∞ (3) and the crystal-to-crystal transformation is reversible between 1 and 3. The release of DMF molecules from 1 results in the metal-organic framework of [Sr(µ-BDC)]∞ expanding a little along the a- and b-axes. The crystal structure optimizations for 1 and 3 disclosed that the lattice expansion is associated with the alternations of the bond distances and angles in the Sr(2+) ion coordination sphere along the a- and b-axes directions. The metal-organic framework 3 collapses at temperatures of more than 600 °C; such an extremely high thermal stability is related to the closed-shell electronic structure of the Sr(2+) ion, namely, the coordinate bond between the closed-shell Sr(2+) ion and the bridged BDC(2-) ligands does not have a preferred direction, which is favored for reducing lattice strains and is responsible for the higher thermal stability. The comparative investigations for the dielectric and ferroelectric behaviors of 1 and 3 confirmed that the motion of the polar DMF molecules, but not the [Sr(µ-BDC)]∞ framework, is responsible for the ferroelectric properties of 1.