Three-Dimensional Synthons for Cage-Dense Inorganic Polymers and Materials

Abstract

The relationship between the monomer structure and polymer properties is central to materials science. Here we discuss the notion of monomer dimensionality, as it refers to the presence of 1-dimensional chains, 2-dimensional rings, or 3-dimensional cages in inorganic polymers. We first highlight ring-containing systems, followed by classical 3-dimensional inorganic monomers (carboranes and polyhedral oligomeric silsesquioxanes, POSS). We then outline our development of modularly accessible phosphorus− nitrogen (PN) cages into polymerizable synthons to access linear or networked inorganic materials. Finally, we summarize the most important obstacles to advancement in the field and point toward areas where the most impactful discoveries are expected. Throughout the Perspective, an emphasis is placed on the properties that emerge when three-dimensional inorganic cages are present in the main chain, particularly as they contrast with materials containing monomers of lower dimensionality.

Constraining Flexibility in the MIL-88 Topology through Integration of 3-Dimensional Linkers

“…Upon rotation, 2DLs extend nonuniformly into the pore space, often resulting in significant deviations in pore size (Figure ). However, 3-dimensional linkers (3DLs) are ditopic linkers with sterically bulky cores that have greater than 2-fold symmetry. ,, Utilizing a 3DL can limit the effects of linker rotation on the local pore environment as the space occupied by a 3DL is independent of its orientation within the pore. In this way, increasing linker dimensionality can limit local flexibility (linker rotation or thermal expansion) in a structure (Figure ).…”

Rigid PN cages as 3-dimensional building blocks for crystalline or amorphous networked materials

“…5 The unique advantages of incorporating high-dimensionality cage linkers into networked materials, particularly MOFs, have recently been noted, motivating the search for new families of 3-D synthons. 5,6 In particular, inorganic synthons that are easy to derivatize and feature a responsive solid-state spectroscopic handle would be broadly useful for the field. As a result, there has been considerable prior interest in the use of phosphorus-nitrogen (PN) containing 1-D (linear) and 2-D (cyclic) synthons for assembling coordination polymers and MOFs.…”