Anion-Directed Assemblies of Cationic Metal–Organic Frameworks Based on 4,4′-Bis(1,2,4-triazole): Syntheses, Structures, Luminescent and Anion Exchange Properties

Three cationic metal–organic frameworks (MOFs), Ag­(btr)·​PF6·​0.5CH3CN (1), Ag2(btr)2­(H2O)·​2CF3SO3·​H2O (2), and Ag2(btr)2­(NO3)·​NO3 (3), were prepared from reaction of 4,4′-bis­(1,2,4-triazole) (btr) with silver salts containing different anions. Complex 1 is a three-dimensional (3-D) framework constructed from tetrahedral-shaped nanoscale coordination cages with PF6– as counteranions. 2 and 3 are 3-D architectures containing 1-D channels, in which charge-balancing CF3SO3– and NO3– are located in their respective channels. Luminescent emission of 1–3 shows an obvious red shift compared with the btr ligand. Anion exchange studies show that 1 is able to selectively exchange MnO4– in aqueous solution with a modest capacity of 0.56 mol mol–1; the luminescent emission of 1 is quickly quenched upon MnO4– exchange.