Two-dimensional coordination polymers containing permethylated motifs - promising candidates for 2D emerging materials. Structural, behavioral and functional particularities

Abstract

Although three-dimensional metal-organic frameworks (3D MOFs) currently enjoy great attention in the scientific world due to their utility to address challenges concerning energy, environment cleaning and not only, very recently two-dimensional version of these, rather considered two-dimensional coordination polymers (2D CPs), have become of interest from the perspective of their approach as ultra-thin layered 2D materials. Different from the emerging 2D materials that are generally inorganic in nature (graphene or 2D allotropes of various elements, MXenes, etc.), 2D CPs contain both inorganic and organic blocks, offering wider possibilities for structural diversification and area of applicability. However, in the crystallization process, 2D CP layers often stack on the basis of intermolecular interactions, leading to higher dimensional materials, which limit the manifestation of the size-effect properties. Their isolation individually or in multilayers with thickness/surface aspect ratio as small as possible is a challenge that seeks solutions through top-down or bottom-up approaches, each of them having certain limits. An original pathway consists in the use of a permethylated ligand with lower surface energy which, through its orientation in the coordination process to the metal ion, favors the anisotropic growth of the polymer and ensures the shielding of the formed nanosheet structure preventing the establishment of noticeable interlayer interactions. Such unique two-dimensional coordination polymers recently reported by the authors and some new data about them are reviewed here from the perspective of their structural particularities, properties, reactivity, functionality, and reusability/recyclability potential.