Pyromellitate Ligand as Building Blocks in the Synthesis of Metal–Organic Frameworks with Hydroxyalkylamines

Abstract

Metal−organic frameworks (MOFs) are an extremely promising and rapidly growing class of coordination compounds. Pyromellitic acid (H 4 Prm) containing four carboxyl groups is a popular ligand for building MOFs. In this study, a twostep approach was used to synthesize MOFs containing polydentate pyromellitate and hydroxyalkylamine ligands. In the first stage, Cu(II), Co(II), and Ni(II) pyromellitates were synthesized by the reaction of sodium pyromellitate with inorganic Cu(II), Co(II), and Ni(II) salts in water. X-ray diffraction showed that the interaction of cobalt nitrate with Na 4 Prm leads to the formation of MOFs based on a heteronuclear polymer complex [Co 3 (μ-ONa) 6 (Prm) 3 (H 2 O) 18 ] n . In the second stage, the interaction of the synthesized pyromellitates with tris(2hydroxypropyl)amine (TPA), tris(hydroxymethyl)aminomethane (TRIS), and bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane (BIS-TRIS) was studied. We describe the synthesis and spectroscopic and thermal properties of nine new complexes. The structure of the complexes [Co 2 (PRM)(BIS-TRIS) 2 ](H 2 O) 5 ( 6) and [Ni 2 (PRM)(BIS-TRIS) 2 ](H 2 O) 3 (9) was studied by X-ray diffraction supplemented by the Hirshfeld surface analysis and density functional theory (DFT) methods. The potential of using the complexes as adsorbents for lead ions has been demonstrated.