In light of the chemical exploitation of CO 2 , new reusable materials for efficiently catalyzing the cycloaddition of CO 2 and epoxides under moderate conditions are needed. Herein, a new series of isostructural metal−organic frameworks (MOFs) M 2 (EDOB) [EDOB 4− = 4,4′-(ethyne-1,2-diyl)bis(2-oxidobenzoate), M = Mg, Ni, Co, Zn, Cu, Fe], known as M-MOF-184, analogous to a well-studied MOF-74 structure, were synthesized and fully characterized. The M-MOF-184 (M = Mg, Co, Ni, Zn) frameworks exhibit accessible mesopore channels (24 Å) and high porosity. Among them, Mg-MOF-184 demonstrated the most upper surface area (>4000 m 2 g −1 ) in any reported MOF-74-type frameworks. Furthermore, Co-MOF-184 revealed the highest CO 2 uptake (73 cm 3 g −1 , at 298 K), and Zn-MOF-184 showed the highest catalytic activity upon the cycloaddition of CO 2 (96% conversion, 86% selectivity, and 82% yield) under mild conditions (1 atm CO 2 , 80 °C, 6 h, and solvent-free). Notably, the catalytic performance of Zn-MOF-184 outperformed that of the original M-MOF-74 (M = Mg, Co, Zn) materials and various Zn-based MOFs. To evaluate the acidity and basicity of a series of M-MOF-184 (M = Mg, Co, Ni, Zn) frameworks, the interaction of these MOFs with acetonitrile vapor was investigated by vapor adsorption and ATR-FTIR spectroscopy measurements. As such, Zn-MOF-184 showed the strongest Lewis acidity derived by Zn cations, which was correlated to the highest catalytic activity upon the cycloaddition of CO 2 . Interestingly, the 2-oxidobenzoate anions from Co-MOF-184 showed the strongest basicity among the series, which was associated with the highest saturated acetonitrile uptake (544 cm 3 g −1 at 298 K). Our findings suggest that the integration of Lewis acidic and basic sites, high surface area, and large accessible pores into the framework can facilitate the CO 2 fixation reaction.

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The Nafion® electrolyte membrane, which provides a proton pathway, is an essential element in fuel cell systems. Thermal treatment without additional additives is widely used to modify the mechanical properties of the membrane, to construct reliable and durable electrolyte membranes in the fuel cell. We measured the microscopic mechanical properties of thermally annealed membranes using atomic force microscopy with the two-point method. Furthermore, the macroscopic property was investigated through tensile tests. The microscopic modulus exceeded the macroscopic modulus over all annealing temperature ranges. Additionally, the measured microscopic modulus increased rapidly near 150 °C and was saturated over that temperature, whereas the macroscopic modulus continuously increased until 250 °C. This mismatched micro/macroscopic reinforcement trend indicates that the internal reinforcement of the clusters is induced first until 150 °C. In contrast, the reinforcement among the clusters, which requires more thermal energy, probably progresses even at a temperature of 250 °C. The results showed that the annealing process is effective for the surface smoothing and leveling of the Nafion® membrane until 200 °C.

Direct urea fuel cells have been recognised as a potential approach for sustainable development. However, the low catalytic activity of urea oxidation has hindered its practical application. Herein, by employing...

Fe, Ni, and Co and their alloys are widely studied for oxygen evolution reaction and hydrogen evolution in electrocatalytic water splitting under alkaline conditions, and their pentlandite sulfide was found to enhance the catalytic activity for the reactions. In this study, the synthesis of pentlandite sulfide of Fe, Ni, and Co was tried by a ball milling and subsequent pyrolysis. It was proved that the ball milling method is a promising way for a pentlandite formation and simultaneous carbon encapsulation. An aniline monomer played a role of carbon source for carbon encapsulation, and ammonium persulfate provided sulfur for a sulfide formation. Three kinds of compounds were synthesized by varying the Ni/Co ratio, and their structural characteristics and electrochemical activity were investigated and compared each other. X-ray diffraction patterns showed that they consisted of pentlandite sulfide and metal alloy phase. Transmission electron microscopy revealed that nanoparticles enwrapped by carbon shell were uniformly distributed on N-doped carbon.Electrochemical activity was studied under alkaline condition, and the overpotential of 260 mV at 10 mA/cm 2 was obtained in 1 M KOH solution for oxygen evolution reaction. After 500 cycles, the overpotential increased slightly to 310 mV. From this study, it was revealed that the electrochemical activity of (Fe, Ni, Co) 9 S 8 depends on structural parameters not elemental composition.