pH-controlled assembling of POM-based metal–organic frameworks for use as supercapacitors and efficient oxidation catalysts for various sulfides

Abstract

The development of electrode materials for supercapacitors is a significant issue for future energy storage devices. In addition, the selective oxidation of sulfides to sulfoxides that serve as key intermediates for synthesizing medically and chemically active molecules is still a critical challenge. In this study, two novel 3D POM-based metal–organic frameworks, formulated as [Cu₃(bty)₃][BW₁₂O₄₀]·4H₂O (1) and [Cu_2.5(bty)₅][BW₁₂O₄₀]·7H₂O (2) (bty = bis(1,2,4-triazol-1-yl)ethane), were obtained via a one-step synthesis strategy by adjusting the pH value under solvothermal conditions. In compound 1, {BW₁₂} as a 2-connected node is located between 2D Cu–organic sheets to yield a novel 3D POM-based metal–organic framework. There are 1D channel structures constructed with Cu–organic sheets in compound 2. Then, {BW₁₂} as a 4-connected node merged into the orifice of the Cu–organic framework forming a glamorous 3D framework. Moreover, the 3D Cu–organic framework of 2 displays the fascinating shape of vase structures. These two compounds could be applied as electrode materials for supercapacitors with specific capacitances of 214.59 F g⁻¹ and 189.17 F g⁻¹ at 0.48 A g⁻¹ respectively, as well as efficient heterogeneous catalysts for selective oxidation of sulfides to their corresponding sulfoxides.