Big Holey Metal-organic Frameworks

In the menagerie of porous materials, examples of metal-organic frameworks typically have been limited to those in the microporous range-with minute pores of 3 nm in diameter or less. Introducing larger cavities into these compounds tends to destabilize the complex coordination between the metal ions and their ligands. Now, chemists in South Korea have managed to expand metal-organic lattices into the mesoporous range, creating a framework of fused cages with pores measuring 3.9 and 4.7 nm in diameter. A team led by Jaheon Kim of Soongsil University created the material, which is composed mainly of Tb³⁺ ions and tripodal carboxylate ligands (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200702324). The researchers synthesized the lattices via a solvothermal reaction between triazine-1,3,5-tribenzoic acid and Tb(NO₃)₃•5H₂O in a mixture of N,N-dimethylacetamide, methanol, and water. They determined the cages' structures (one cage shown) by using X-ray crystallography. According to the researchers, the material's high thermal stability and its ability to remain rigid under vacuum make it a good framework for hosting other molecules.