Metal-organic frameworks (MOFs) are a class of crystalline materials composed of metal ions or clusters (nodes) and organic ligands (linkers) that have unique properties stemming directly from the connecting geometry of these nodes and linkers. A simplified depiction of MOF construction is shown in Figure . Perhaps the most iconic property of MOFs is their potential porosity. In fact, the IUPAC definition of a MOF is "a coordination network with organic ligands containing potential voids." These voids (pores) range in diameter from approximately 0.3 nm to greater than 2 nm. An example is given in Figure , which shows the pores of the MOF Cu2(btc)3 (commonly termed "HKUST-1"; btc = 1,3,5-benzene tricarboxylate). The presence of empty pores leads to very high internal surface areas (SAs) -MOFs with SA greater than 7000 m 2 /g have been reported