Metal nodes and metal sites in metal–organic frameworks

In this chapter, a brief introduction is given to some of the more common coordination complexes that make up connecting nodes in the increasingly ubiquitous field of metal organic frameworks (MOFs). A specific focus is directed on those motifs which allow for the generation of open metal sites within these microporous crystalline frameworks, specifically in the case of MOFs containing carboxylate-based organic linkers. Some of the proposed and upcoming applications of open metal sites in MOFs are discussed, along with select examples where the host–guest interaction of the framework with a substrate molecule is mediated by metal-bridging ligands such as hydroxide. Particular attention is given to introducing those studies which seek to investigate the variation in guest binding as a function of changing metal ions within the frameworks. Finally, several examples of catalysis in MOFs are presented, demonstrating the utility of open metal sites within such frameworks and highlighting the potential advantages of pore control over more traditional heterogeneous catalysts.