[M₃(μ₃-O)(O₂CR)₆] and related trigonal prisms: Versatile molecular building blocks for crystal engineering of metal-organic material platforms

This review details the emergence of metal-organic materials (MOMs) sustained by high symmetry trigonal prismatic molecular building blocks (MBBs). MOMs have attracted general attention over the past two decades as judicious selection of MBBs allows crystal engineers to exert exquisite control over MOM structure, which, when combined with their modularity, diverse composition and fine-tuneable structural features, makes their properties controllable in a manner uncommon in materials science. In this context, tetrahedral and octahedral MBBs, which readily afford diamondoid (dia) or primitive cubic (pcu) nets, respectively, are the most commonly studied MBBs. However, trigonal prismatic MBBs have also captured the imagination of crystal engineers since they can sustain stable, high symmetry, extra-large surface area nets with new topologies and exhibit excellent gas sorption performance. Nets formed by linking [M₃(μ₃-O)(O₂CR)₆] MBBs are of particular interest and are discussed from a crystal engineering perspective. These MBBs can form discrete (0-D) polyhedra, 2-D grids and 3-D nets that represent families or "platforms" that enable systematic studies of structure-property relationships. The development of decorated [M₃(μ₃-O)(O₂CR)₆] MBBs that facilitate a 2-step strategy for generation of novel MOM platforms from simple, low cost MBBs, is also discussed.