Design and Applications of Spherical Infinite Coordination Polymers (ICPS)

Since Alfred Werner published his work on coordination compounds in 1893, much progress has been made regarding this class of materials. Further studies evolved to the coordination polymers, among which the Metal-Organic Frameworks (MOFs), which are two- or three-dimensional coordination networks containing potentially empty cavities. Frequently, MOFs are crystalline materials with the coordination units repeating itself in an ordered manner in the structure, thus creating different topologies. However, synthetic parameters (pH, temperature, solvent) directly influence the kinetics and thermodynamics of the nucleation and growth of MOF crystals. In some cases, a material of low crystallinity may be formed, with short-range order. Most authors classify these compounds as Infinite Coordination Polymers (ICPs), Coordination Polymer Particles (CPPs) or Nanoscale Coordination Polymers (NCPs). Although not yet standardized by IUPAC, several articles, including recent review articles, name low-crystalline coordination polymers as ICPs. ICPs can show high tailorability regarding the particle size and morphology. They are usually obtained as micro- or nanoparticles, with spherical (mainly), cubic, rod-like and ring-like morphologies being reported. The major challenge in the study of ICPs lies in the structural elucidation, often performed by single crystal X-ray diffraction in crystalline MOFs. In this chapter, the synthetic routes, formation mechanisms, characterization techniques and potential applications of spherical ICP particles, such as in sensing, light-emitting devices, biomedicine, catalysis, gas sorption and separation, will be discussed.

Keywords

Coordination chemistry, Infinite coordination polymers, Metal-Organic frameworks, Multitopic organic ligands, Spherical morphology, Transition and lanthanide metal ions