Additive Effects in the Formation of Fluorescent Zinc Metal–Organic Frameworks with 5‑Hydroxyisophthalate

Three new metal–organic frameworks (MOFs) are formed from the reaction of zinc with 5-hydroxyisophthalic acid (H₃-5-hip) with a range of additives in dimethylformamide (DMF). The additives include water, pyridine, and [Me_<i>n</i>NH_4–<i>n</i>]Cl (<i>n</i> = 0–4) and, through hydrogen bonding, have a marked effect on the formation and phase of any resultant MOF, often in a narrow range of substoichiometric concentrations. The three MOFs, [Me₂NH₂]­[Zn₂(5-hip)­(H-5-hip)­(H₂O)]·3.25DMF (<b>1</b>), α-[Me₂NH₂]₂[Zn₂(5-hip)₂]·2DMF (<b>2</b>), and [Me₂NH₂]­[Me₄N]₂[Zn₄(5-hip)₂(H-5-hip_2.5)]·3DMF (<b>3</b>), have solvent-accessible pores, and the flexibility of the MOFs allows relaxation from a porous state to minimize the void space on desolvation. Topological analysis of the frameworks reveals two previously unrecorded MOF topologies. Compounds <b>2</b> and <b>3</b> are fluorescent, while this property is absent in compound <b>1</b>. We also present a revised structure for the closely related β-[Me₂NH₂]₂[Zn₂(5-hip)₂]·2DMF (<b>4</b>)