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4216310 
Journal Article 
Separation of hexane isomers in a metal-organic framework with triangular channels 
Herm, ZR; Wiers, BM; Mason, JA; van Baten, JM; Hudson, MR; Zajdel, P; Brown, CM; Masciocchi, N; Krishna, R; Long, JR 
2013 
1 
Science
ISSN: 0036-8075
EISSN: 1095-9203 
American Association for the Advancement of Science 
340 
6135 
960-964 
English 
23704568 
WOS:000319344100042 
Metal-organic frameworks can offer pore geometries that are not available in zeolites or other porous media, facilitating distinct types of shape-based molecular separations. Here, we report Fe2(BDP)3 (BDP(2-) = 1,4-benzenedipyrazolate), a highly stable framework with triangular channels that effect the separation of hexane isomers according to the degree of branching. Consistent with the varying abilities of the isomers to wedge along the triangular corners of the structure, adsorption isotherms and calculated isosteric heats indicate an adsorption selectivity order of n-hexane > 2-methylpentane > 3-methylpentane > 2,3-dimethylbutane ≈ 2,2-dimethylbutane. A breakthrough experiment performed at 160°C with an equimolar mixture of all five molecules confirms that the dibranched isomers elute first from a bed packed with Fe2(BDP)3, followed by the monobranched isomers and finally linear n-hexane. Configurational-bias Monte Carlo simulations confirm the origins of the molecular separation.