Size-Selective Sorption of Small Organic Molecules in One-Dimensional Channels of an Ionic Crystalline Organic-Inorganic Hybrid Compound Stabilized by π-π Interactions

摘要

The design and syntheses of porous materials such as zeolites and metal-organic frameworks (MOFs) are areas of intense research because of their unique properties in gas storage, separation, and heterogeneous catalysis. Crystalline micro-porous zeolites show shape-selective adsorption properties because the sizes of the channel apertures formed by the covalently bonded [TO4] (T = Si, Al, P, Ti, etc.) and/or [MO6] (M = V, Mn, Mo, etc.) units can be controlled. In contrast, the pore sizes of MOFs, which are constructed from coordinatively bonded metal ions and organic ligands, can be controlled by the lengths and functional groups of organic ligands. In particular, the use of aromatic units induces π-π interactions and enables the rational control of the complexation of the building units. In addition, the presence of the aromatic moieties means that the resulting framework would show unique structural and guest-sorption properties. For example, the guest sorption in a Cu~(II) dihydroxybenzoate/4,4'-bipyridine MOF causes the gliding of π-π-stacked building units, which leads to the change in the framework structure, and a Co~(II) benzenetricarboxylate MOF separates the aromatic units from the aliphatic hydrocarbons.