2D → 3D corrugated structure self-assembled from 4,4′-methylenebis(N-(pyridin-2-ylmethylene)aniline and terephthalic acid: Crystal structure and selective anion separations via anion exchange

A new flexible cationic Zn(II)metal organic framework, {[Zn-2(BDC)(1.5)(L)(DMF)]NO3 center dot DMF center dot solvent}(n), MOF 1, which is a corrugated two-dimensional network, was synthesized by self-assembly of Zn(NO3)(2).6H(2)O with 4,4 '-methylenebis(N-(pyridin-2-ylmethylene)aniline as a neutral ligand and terephthalic acid in dimethyl formamide (DMF) as solvent and characterized by X-ray diffraction. Because of the presence of uncoordinated nitrate (NO3-) ions in the channels, the compound was employed for ion-exchange applications. We report a detailed study of the host-guest interaction for a cationic metal-organic framework (MOF) that can reversibly capture nitrate. The recrystallization of the MOF was evaluated by monitoring the anion exchange dynamics using a combination of powder X-ray diffraction and Fourier transform infrared spectra with various kinds of foreign anions. This MOF showed fast and highly efficient Cr2O72- and CrO42-, N-3(-), MnO4-, and SCN- exchange. The trapping capacities of Cr2O72-, CrO42-, N-3(-), MnO4-, and SCN- were 105,138, 44,104, and 25mg/g at 25 degrees C after 3h, respectively, and there was good recyclability for capturing N-3(-) and SCN-. {[Zn-2(BDC)(1.5)(L)(DMF)]NO3}(n) exhibited anion exchange selectivity of SCN- in a solution containing a mixture of 0.025mmol N-3(-), SCN-, CrO4-2-, Cr2O72-, and MnO4- for 3h and exhibited anion exchange selectivity for SCN- and Cr2O72- in a solution containing a mixture of 0.001mmol N-3(-), SCN-, CrO42-, Cr2O72-, and MnO4-.