Four New Three-Dimensional Polyoxometalate-Based Metal–Organic Frameworks Constructed From [Mo6O18(O3AsPh)2]4– Polyoxoanions and Copper(I)-Organic Fragments: Syntheses, Structures, Electrochemistry, and Photocatalysis Properties

Abstract

Four novel polyoxometalate-based copper(I)-organic frameworks, namely, [Cu(I)(2)(cis-L1)(2)][Cu(I)(2)(trans-L1)(2)Mo(6)O(18)(O(3)AsPh)(2)] (1), [Cu(I)(4)(L2)(4)Mo(6)O(18)(O(3)AsPh)(2)] (2), [Cu(I)(4)(L3)(4)Mo(6)O(18)(O(3)AsPh)(2)] (3), and [Cu(I)(4)(L4)(2)Mo(6)O(18)(O(3)AsPh)(2)] (4) (L1 = 1,3-bis(1,2,4-triazol-1-yl)propane, L2 = 1,4-bis(1,2,4-triazol-1-yl)butane, L3 = 1,5-bis(1,2,4-triazol-1-yl)pentane, and L4 = 1,6-bis(1,2,4-triazol-1-yl)hexane), have been successfully synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, infrared spectra (IR), UV-vis spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Compound 1 is composed of two crystallographically independent and distinct polymeric motifs: one-dimensional (1D) S-shaped chain and two-dimensional (2D) undulated layer. The S-shaped chains penetrated into the 2D parallel layers to generate an unusual 1D + 2D → three-dimensional (3D) polypseudo-rotaxane framework. In 2, the As(2)Mo(6) polyoxoanions in tetradentate modes link four neighboring -L2-Cu-L2- chains to produce a rare 3D trinodal (3,4)-connected self-penetrated framework with Point Symbol of (8(3))(2)(8(2)·12(4)). In 3, adjacent Cu(I) atoms are linked by As(2)Mo(6) polyoxoanions and L3 ligands into a 2D layer. The layers are further interlocked by the two nearest neighboring ones to form a 3D polycatenated framework. In 4, L4 ligands bridge four Cu(I) atoms to yield 2D wavelike layers, which are further linked by the octadentate As(2)Mo(6) polyoxoanions to form a 3D tetranodal (3,4,6)-connected framework with Point Symbol of (6(3))(4·6(3)·8(2))(6(4)·8(2))(4(2)·6(2)·8(10)·10). In addition, the photocatalytic activities of compounds 1, 3, and 4 for decomposition of methylene blue (MB) under UV light have been investigated. Moreover, their electrochemical properties have also been studied in 1 M H(2)SO(4) aqueous solution.