Metal-Organic Frameworks Based on Previously Unknown Zr8/Hf8 Cubic Clusters

The ongoing study of zirconium- and hafnium-porphyrinic metal-organic frameworks (MOFs) led to the discovery of isostructural MOFs based on Zr-8 and Hf-8 clusters, which are unknown in both cluster and MOF chemistry. The Zr8O6 cluster features an idealized Zr-8 cube, in which each Zr atom resides on one vertex and each face of the cube is capped by one mu(4)-oxygen atom. On each edge of the cube, a carboxylate from a porphyrinic ligand bridges two Zr atoms to afford a 3D MOF with a very rare (4,12)-connected ftw topology, in which two types of polyhedral cages with diameters of similar to 1.1 and similar to 2.0 nm and a cage opening of similar to 0.8 nm are found. The isostructural Zr- and Hf-MOFs exhibit high surface areas, gas uptakes, and catalytic selectivity for cyclohexane oxidation.