Flexible porous coordination polymers constructed from 1,2-bis(4-pyridyl)hydrazinevia solvothermal in situreduction of 4,4′-azopyridine

Abstract

Solvothermal reactions of Zn(NO₃)₂, 1,4-benzenedicarboxylic acid (H₂bdc), and 4,4′-azopyridine (azpy) in different conditions yielded [Zn(bdc)(bphy)]·DMF·H₂O (1a, bphy = 1,2-bis(4-pyridyl)hydrazine, DMF = N,N-dimethylformamide) and [Zn(bdc)(bphy)]·EtOH·H₂O (1b) with two-fold interpenetrated dmp topology and [Zn₂(bdc)₂(bphy)]·1.5EtOH·H₂O (2a) and [Zn₂(bdc)₂(bphy)]·DMA·1.5H₂O (2b, DMA = N,N-dimethylacetamide) with two-fold interpenetrated pcu topology. The in situreduction of azpy to bphy was confirmed by single-crystal structures and LC-MS analyses of the acid-digested crystalline samples, as well as controlled solvothermal experiments. Removal of the guest molecules in 1a/1b and 2a/2b converts the materials to guest-free phases [Zn(bdc)(bphy)] (1) and [Zn₂(bdc)₂(bphy)] (2), respectively, which were identified by PXRD. CO₂ sorption experiments performed at 195 and 298 K showed low porosity for 1 and gated sorption behavior for 2. At 298 K, 2 exhibits high selectivity for adsorbing CO₂ over CH₄.