Cu-3(BTC)(2) nanoflakes synthesized in an ionic liquid/water binary solvent and their catalytic properties

Low-dimensional metal-organic frameworks (MOFs) exhibit enhanced properties compared with three-dimensional (3D) geometry MOFs in many fields. In this work, we demonstrate the synthesis of Cu-3(BTC)(2) (BTC = benzene-1,3,5-tricarboxylate) nanoflakes in a binary solvent of ionic liquid (IL) and water. Such a MOF architecture has a high surface area and abundant unsaturated coordination metal sites, making them attractive for adsorption and catalysis. For example, in catalyzing the oxidation reactions of a series of alcohols, the Cu-3(BTC)(2) nanoflakes exhibit a high performance that is superior to Cu-3(BTC)(2) microparticles synthesized in a conventional solvent. Experimental and theoretical studies reveal that the IL accelerates the crystallization of Cu-3(BTC)(2), while water plays a role in stripping the Cu-3(BTC)(2) blocks that are formed at an early stage through its attack on the crystal plane of Cu-3(BTC)(2). Such an in situ crystallization-exfoliation process that uses an IL/water solvent opens a new route for producing low-dimensional MOFs.