Biomimetic And Extreme Surface-Area Frameworks

Two developments in the area of metal-organic framework (MOF) compounds may broaden commercialization and range of application of this class of porous crystals, which are composed of metal clusters joined by organic linkers. In one study, a team led by Texas A&M University chemists Zhi-Yuan Gu, Dawei Feng, and Hong-Cai Zhou used hemelike Fe-carboxyphenyl porphyrin units, which resemble enzyme cofactors, to link Zr₆ clusters, forming a large-channel (3.7-nm diameter) MOF with exceptional stability in aqueous media. The team used the enzyme mimic to catalyze oxidation of pyrogallol and other common test compounds with hydrogen peroxide and measured high levels of catalytic activity and chemical selectivity (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201204475). In the other study, researchers including Northwestern University’s Omar K. Farha and Joseph T. Hupp have synthesized two new MOFs from copper clusters and paddle-wheel-shaped carboxylate linkers that exhibit record-setting surface areas of just over 7,000 m² per gram, as measured by a standard gas-uptake method. The high surface areas, which are crucial for gas storage applications, surpass the recent record—6,000 m²/g (J. Am. Chem. Soc., DOI: 10.1021/ja3055639). The team showed computationally that by tailoring the organic ligands, MOFs can reach surface areas as high as 14,600 m²/g.