Ln-MOFs using a compartmental ligand with a unique combination of hard–soft terminals and their magnetic, gas adsorption and luminescence properties

Abstract

The present work is part of our ongoing quest for developing multifunctional lanthanide–organic hybrid materials using non-conventional soft N-rich pyridyl–pyrazole-based ligands. Accordingly, we have embarked on an interesting venture of generating lanthanide-metal–organic frameworks (MOFs) using a new N-rich compartmental type ligand. It is imperative to note that compartmental ligands are seldom used in MOF synthesis, let alone lanthanide-MOFs. The terminals of the newly designed titular ligand comprise two contrasting functional moieties, a hard carboxylic group and a soft chelating pyridyl–pyrazole moiety. Their contrasting coordination behaviours are manifested in two isostructural lanthanide-based MOFs (Ln = Gd (1), Dy (2)). Single crystal X-ray analyses reveal archetypal graphite-like framework formation containing substantial pores inside the network with a corresponding moderately high surface area and N₂ and CO₂ gas sorption properties. Another important aspect of lanthanide-MOFs is magnetism and the results of the present work are highly encouraging. The occurrence of the magnetocaloric effect (MCE) of mononuclear Gd-based MOF-1 further boasts the notion of generating magnetic materials. Dy-based MOF-2, on the other hand, features single ion magnet (SIM) behavior, as further confirmed by ac susceptibility measurements.