Polyoxometalate-directed assembly of various multinuclear metal-organic complexes with 4-amino-1,2,4-triazole and selective photocatalysis for organic dye degradation

A series of polyoxometalate (POM)-based metal-organic complexes containing multinuclear Cu(II) clusters with a 4-amino-1,2,4-triazole (4-atrz) ligand, namely, [Cu-3(4-atrz)(8)(PMo12O40)(2)(H2O)(2)]center dot 2H(2)O (1), [Cu-2(4-atrz)(6)(SiW12O40)(H2O)]center dot 6H(2)O (2), [Cu-2(4-atrz)(4)(mu(2)-OH)(CrMo6(OH)(6)O-18)]center dot 3H(2)O (3), [Cu-3(4-atrz)(3)(Mo8O27)(H2O)(4)]center dot 6H(2)O (4) and [Cu-3(4-atrz)(3)(V10O30)(0.5)(mu(3)-OH)(H2O)]center dot H2O (5) have been synthesized by selectively adding additional citric acid or boric acid under hydrothermal conditions and have been structurally characterized by single-crystal X-ray diffraction and powder X-ray diffraction. Compound 1 has a zero-dimensional (0D) architecture, which is constructed from a linear trinuclear cluster [Cu-3(4-atrz)(8)(H2O)(2)](6+) and two Keggin PMo12O403- anions. Compound 2 shows a 1D zigzag chain, in which the binuclear [Cu-2(4-atrz)(6)(H2O)](4+) clusters and Keggin SiW12O404- anions connect to each other. Compound 3 is a 1D linear chain based on linear [Cu-3(4-atrz)(6)](6+) clusters; the [CrMo6(OH)(6)O-18](3-) anions hang on two sides of the 1D chain. Compound 4 has a 2D layer constructed from trigonal [Cu-3(4-atrz)(3)(H2O)(4)](6+) clusters and rare infinite [Mo8O27](n)(6n-) chains. The [Mo8O27](6-) anion is transformed from the Anderson-type [CoMo6(OH)(6)O-18](3-) anion, which is also rare in the POM-based reaction system. Compound 5 has a 3D framework constructed from trigonal trinuclear [Cu-3(4-atrz)(3)(OH)](5+) clusters and rare [V10O30](10-) polyanions, which represents the first example of a V10O30-based 3D metal-organic complex. Structural analyses indicate that different POMs show great effect on the various structures of 1-5 and the additional acids play an important role in the formation of 1-5. Photocatalytic experiments of 1-5 on degradation of three organic dyes (methylene blue, Rhodamine B and methyl orange) manifest that compounds 1-3 are good candidates for the photocatalytic degradation of methylene blue, and compound 1 is a good photocatalyst for the degradation of Rhodamine B.