Metallocycle-Supported POM-Based Metal-Organic Frameworks Assembled from Isomeric N-Rich Ligands: Structures and Selective Adsorption and Separation of Cationic Dyes

摘要

Two novel POM-based metal-organic frameworks, [Ag-7(L-1)(2)(mu(2)-OH)(4)][H3VW12O40] (1) and [Ag-8(L-2)(4)][VW12O40]4H(2)O (2) have been isolated by altering the isomeric organic ligands {5-[n-(1,2,4-triazol-4-yl)phenyl]-1H-tetrazole: n = 3 (HL1); n = 4 (HL2)} under hydrothermal conditions. Due to L-1 acts as a V-shaped linker, compound 1 displays a 3D MOF with three types of metallocycles, in which the Keggin polyanions locat in the largest metallocycle (the size of void ca. 13.31 angstrom x13.53 angstrom). However, when the ligand is replaced by straight ligand L-2, compound 2 with a different structure is obtained. Although compound 2 is also a 3D MOF, the types of metallocycle are reduced to one. The Keggin polyanions are seated in the only metallocycle (the size of void ca. 13.6 angstrom x13.7 angstrom). In addition, the adsorption behaviors of the title compounds for organic dyes were investigated in detail. In particular, compound 1 could selectively separate MB+ from the mixture of MB+/RhB+ and MB+/MO- within 5 min, which can be used as a chromatography column for dyes removal.