Zeolite-Like Frameworks Have Large Cavities

A process for synthesizing metal-organic frameworks offers the potential for introducing tunable organic functionalities into large zeolite-like cavities, according to Mohamed Eddaoudi of the University of South Florida and coworkers (Chem. Commun., published online Feb. 2, dx.doi.org/10.1039/b600188m).

The team used a molecular building block approach to construct two novel zeolite-like metal-organic frameworks (ZMOFs) by bridging tetrahedral building units containing indium(III) ions (green) with doubly deprotonated 4,5-imidazoledicarboxylic acid linkers in the presence of a structure-directing agent such as protonated imidazole. One of the frameworks (shown, cavity is yellow)—called sod-ZMOF—has a sodalite zeolite-type topology with each In³⁺ ion coordinated to four nitrogen atoms (blue) and two oxygen atoms (red). The other framework, rho-ZMOF, has the zeolite rho-type topology. Its cavities are "extra-large" compared with those of sod-ZMOF and zeolite analogs.

ZMOFs are anionic, have accessible multidimensional channels and permanent porosity, and exhibit facile ionic exchange capacity. The large cavities and negative charges of the frameworks offer "great potential to explore applications involving the inclusion or encapsulation of large molecules and cations," Eddaoudi says.