Acylhydrazidate-based porous coordination polymers and reversible I2 adsorption properties

Abstract

By employing the hydrothermal in situ acylation of organic acids with N2H4, three porous acylhydrazidate-based Zn2+/Cd2+ coordination polymers as [M(L1)(H2O)]·1.5H2O (H2L1 = benzimidazole-5,6-dihydrazide; M2+ = Zn2+ 1, Cd2+ 2) and [Zn(HL2)(H2O)]·3H2O (H3L2 = 4,5-(di-(3′,4′-phthalhydrazide))) 3 were obtained. X-ray single-crystal diffraction analysis reveals that the frameworks of 1–3 can all be simplified into a (3metal node,3ligand node)-connected net. However, since the ligands are different, they show the distinct structures: a C-tube-like structure for the isostructural 1 and 2; a 103 topology for 3. The cif-checking reports indicate that the solvent accessible voids in the structures of 1–3 are 1055 Å3, 1282.4 Å3, and 978 Å3, respectively. It is noteworthy that 3 is the first example of triacylhydrazidate-based coordination polymer. The investigation of the I2-adsorption property for two Zn2+ compounds suggests that both can adsorb reversibly the I2 molecule. The adsorption amount for 3 (100 mg adsorbing 22.0 mg I2) is a bit higher than that for 1 (100 mg accommodating 15.6 mg I2). However, the adsorption speed for 3 is much faster than that for 1. About 5 s, the I2 adsorption for 3 is close to saturation, while for 1, it is about 20 days. This might be related to the number and the distribution for the uncoordinated N/O atoms on the side walls of the channels. Keywords: Porous coordination polymers, In situ, Acylation, I2 adsorption, Mutilcarboxylic acids