Lanthanide-based metal-organic frameworks (Ln-MOFs): synthesis, properties and applications

Micro- and meso-porous solid materials based on metal-organic frameworks (MOFs) have been gaining significant attention for the last three decades as they offer diverse applications in a large number of areas. An advantage of these materials is that they can be rationally designed with desired characteristics using several metal ions belonging either to the s-, p-, d-, or f-block elements of the periodic table, in combination with suitable polytopic organic linkers (multidentate ligands), resulting in various structural and application aspects. Among the MOFs, those composed of lanthanide ions {Ln(iii)}, commonly referred to as Ln-MOF systems, have attracted enormous attention because they display favorable characteristics, like large structural diversity, tailorable structural designs, tunable porosity, large surface area, high thermal stability, and immense chemical stability. All these characteristics are very useful for their widespread applications in diverse areas. Since Ln(iii) ions possess higher coordination numbers compared to transition metal (TM) ions, Ln-MOF materials are generally more porous, offering better applications. Further, hybrid MOF systems consisting of both Ln(iii) and TM ions (Ln-TM-MOF systems) can introduce additional features to these mixed metal porous materials for their much wider applications. Luminescence and magnetic properties of Ln(iii) ions make these materials ideal for various display and sensing applications, in addition to their porosity-related applications. In this review article, our aim is to discuss the basic aspects, preparation methodologies, important properties, and utilizations of MOF materials with a special emphasis on Ln(iii)-based MOF systems. Initially, a short introduction is provided on MOF systems, which is followed by other aspects of these materials as mentioned above. Subsequently, we sequentially highlight the interesting characteristics of these materials, including their structural aspects, porosity, magnetic properties, and luminescence behavior. Finally, some of the potential uses of these systems have been presented with special emphasis on their gas storage, catalysis and luminescence-based chemical sensing applications.