Ionic liquid-water interfacial synthesis of ionic liquid incorporated metal-organic frameworks with enhanced adsorption properties

In the present work, a two-phase system composed of a hydrophobic ionic liquid (IL) containing copper ions (Cu(II)) and water containing organic linkers was constructed and the Cu-based metal-organic framework (Cu-MOF) formed at the IL-water interfaces at room temperature. The IL 1,3-bis(carboxymethyl)imidazolium chloride ([BCMIM]Cl) was also introduced in the MOF structures via using it as co-linker. The adsorption capacity of the synthesized Cu-MOF and [BCMIM]Cl modified Cu-MOFs was evaluated using the organic dye Congo red (CR) as target compound. Experimental results suggested that the incorporation of [BCMIM]Cl in the Cu-MOF remarkably improved the CR adsorption capacity due to the strong π-π and electrostatic interactions between the cation of [BCMIM]Cl and CR. The adsorption behavior of CR on [BCMIM]Cl modified Cu-MOF fitted well with pseudo-second-order kinetics and Freundlich isotherm model. Thermodynamic analysis suggested the adsorption of CR on [BCMIM]Cl modified Cu-MOF was a physical adsorption process. Finally, compared with reported adsorbents, the [BCMIM]Cl modified Cu-MOF exhibited higher CR adsorption capacity, indicating that it was a promising adsorbent for the removal of organic dyes from water.