A record-breaking crystal 鈥� each gram of which has an internal surface area equivalent to 17 tennis courts 鈥� has been created. The new material is about 40 per cent roomier than the previous record holder.
The substance鈥檚 capaciousness should make it extremely useful as a molecular trap for large molecules, such as pharmaceuticals and petrochemicals, say the researchers at the University of Michigan, Ann Arbor, who made it.
The colourless crystal is a type of Metal Organic Framework and has been named MOF-177. MOFs are made up of alternating organic molecules and metal-containing compounds. The new crystal鈥檚 vast internal space results from the use of an organic molecule called 1,3,5 benzentribenzoate.
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This is a large triangular molecule made of three benzene rings branching off a central benzene ring. The molecules are positioned at the vertices of the tetrahedral zinc oxide-based complexes, an arrangement that yields a very high surface area relative to the crystal鈥檚 volume. The organic component鈥檚 convoluted shape also gives 鈥済uest鈥� molecules that enter the crystal structure lots of edges on which to stick.
Molecular sponge
鈥淢OF-177 has really spectacular properties,鈥� says Pierre Jacobs, a chemist at the Catholic University of Leuven, Belgium. He says the major breakthrough is that the holes within the crystal are large enough to accommodate relatively large molecules, more than one nanometre across.
It could therefore be used to separate different molecules during the chemical manufacture of compounds such as pharmaceuticals, petrochemicals or buckyballs. MOF-177, or related substances, could also find a role as a molecular sponge for storing hydrogen in fuel cells for vehicles, Jacobs suggests.
The new crystal is an improvement over similar compounds, called zeolites, because these can typically only incorporate molecules up to around 0.5 nanometres across, according to Adam Matzger one of the Michigan team.
Perhaps best of all, MOF-177 is disarmingly simple to make 鈥� the researchers just heated the organic molecules and zinc oxide clusters together at 100 掳C.
Journal reference: Nature (vol 427, p 523)