The design and synthesis of mixed ligand metal organic frameworks for xylene inclusion

Abstract

Host-guest chemistry, also known as inclusion chemistry, is an important subfield of supramolecular chemistry where there is great current interest owing to its great promise in the areas of separation of small molecules, sensors, and chiral separation. The term ‘inclusion compounds’ refers to the association between large compounds (host) that is able to enclose a smaller molecule (guest). This association utilizes non-covalent interactions, and the supramolecular entity is known as a “host-guest complex” or supermolecule. The aim of the study is to design and synthesize mixed ligands metal organic frameworks (MOFs) for xylene inclusion. The first part of the study involves the synthesis and characterisation of five pyridine N-donor and O-donor ligands, namely: 2,7-di(pyridin-4-yl)benzo[lmn][3,8]phenthroline-1,3,6,8(2H,7H)tetraone(Lig1), 2,7-bis(pyridin-3-ylmethyl)benzo[lmn][3,8]phenthroline-1,3,6,8(2H,7H)tetraone(Lig2), 2-(pyridin-4-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (Lig3), 2-(pyridin-4-ylmethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (Lig4) and N,N'-bis(glycinyl)pyromellitic diimide (Lig5). The second part involves the synthesis and characterization of MOFs. The MOFs will be synthesized by reacting the pyridine N-donor ligands, carboxylate O-donor co-ligands (fumaric acid; 2.2-bipyridine; 2.2-bipyridine-4.4’-dicarboxylic acid, 4.4’-oxybis(benzoic acid) and 2.6-naphthalenedicarboxylic acid) and transition metal salts in DMF under solvothermal conditions. The synthesized MOFs were characterized using thermogravimetric analysis (TGA), single crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD). Xylene inclusion experiments were performed on the MOFs and the resulting inclusion compounds were characterized using TGA, SCXRD and PXRD.