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

• Published in: European journal of inorganic chemistry Vol. 2019; no. 13; pp. 1839 - 1846
• Main Authors: Liu, Lei, Zhang, Hai‐Yan, Wang, Hai‐Jun, Chen, Song, Wang, Jing‐Han, Sun, Jing‐Wen
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 09-04-2019
• Subjects: Cationic dyes; Column chromatography; Crystal; Dyes separation; Inorganic chemistry; Ligands; Metal-organic frameworks; Metallocycle; Polyelectrolytes; Polyoxometelates; Selective adsorption; Tetrazoles
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201900086

Two novel POM‐based metal‐organic frameworks, [Ag7(L1)2·(µ2‐OH)4][H3VW12O40] (1) and [Ag8(L2)4][VW12O40]·4H2O (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 L1 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 Å × 13.53 Å). However, when the ligand is replaced by straight ligand L2, 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 Å × 13.7 Å). 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.
Two new metallocycle‐supported POM‐based metal‐organic frameworks were isolated by employing isomeric N‐riched rigid organic ligands (straight and the V‐shaped). It is Interesting that both modes can form metallocycles with Ag+ cations and further to incorporate POMs. Obtained compounds could fast and selectively separate MB+ dye molecules from the mixtures of MB+/RhB+ and MB+/MO– for a moment, respectively.