Template metal-organic frameworks: solvent-free synthesis, characterization and powder X-ray diffraction studies of [Cu(NO3)2(bipy)2](py)2

Abstract

A solid-state synthetic method was used for the preparation of template metal-organic frameworks [Cu(NO3)2(bipy)2](py)2] (1a). The compound was prepared by grinding stoichiometric amount of [Cu(NO3)2]·3H2O, 4,4-bipyridine and pyrene in absence of any solvent. Solvent based synthesis of [Cu(NO3)2(bipy)2](py)2 (1b) was also carried out by the reaction of the metal salt and the two ligands by refluxing in methanol for 2 h for comparison purpose. The materials were characterized by elemental analysis, FT-IR, UV–visible spectroscopies and EI-MS, TGA and powder X-ray diffraction (PXRD) analysis. In order to understand the geometry and structure of the compound, the PXRD patterns of the compounds 1a and 1b were compared with the simulated patterns of the single crystal X-ray diffraction data of the analogous isostructural nickel compound [Ni(NO3)2(bipy)2](py)2 obtained from the Cambridge structural database. The PXRD patterns of the synthesized metal-organic frameworks (MOFs) 1a and 1b were in close agreement with the simulated pattern of the single crystal X-ray diffraction data of the nickel compound [Ni(NO3)2(bipy)2](py)2 suggesting that both compounds are isostructural. This study suggests that template MOFs that afford controllable cavities are suitable for accommodating organic guest molecules which can be synthesized by manual grinding of the starting materials. It was also revealed that neutral solids can be effective templates during the formation of square-grid coordination networks with pyrene as guest under mechanochemical conditions.