HYBRIDIZATION OF A LAYERED TITANATE WITH A MOF

Abstract

Although metal-organic frameworks (MOFs) have been extensively investigated for many applications including adsorbents, some MOFs suffer from poor chemical stability lower than other microporous materials like zeolites. Here, we report the hybridization of a prototype MOF, MOF-5 composed of Zn₄O units and benzene linkers, with a layered titanate, K₂Ti₄O₉. The reaction of K₂Ti₄O₉ having zinc acetylacetonate complexes in the interlayer space with MOF-5 precursors including zinc acetate and benzene-1,4-dicarboxylic acid gave the product showing the basal spacing of 2.0 nm in the powder X-ray diffraction pattern, which was larger than that of the starting K₂Ti₄O₉ (0.87 nm). This product, in contrast to the starting K₂Ti₄O₉, had micropores, revealed by the N₂ adsorption isotherm. Scanning electron microscopy showed that the product was composed of belt-like particles with the length of ca. 1 µm like the starting K₂Ti₄O₉ and nanoparticles deposited on the belt-like particles assignable to MOF-5 nanocrystals. The N₂ adsorption isotherms of the products after the exposures of water vapor with different humidities showed that the bare MOF-5 underwent the structural collapse when treated with 10%-water vapor whereas the product retained the structure even after the treatment with 30%-water vapor. These results suggested that unit-cell-thick MOF-5 was immobilized in the interlayer space of K₂Ti₄O₉.