Synthesis of 2D MOF having potential for efficient dye adsorption and catalytic applications

Abstract

Synthesis of 2D MOFs is often sensitive to the reaction conditions like temperature and solvent etc. Cu(II)-5-azidoisophthalate MOF (Cu(II)–5N₃IP) has been synthesized at room temperature as well as under solvothermal conditions. The azide functional group remained stable during solvothermal synthesis at 85 °C. Cu(II)–5N₃IP crystallized in a Kagomé-type structure. Typical Cu₂ paddle-wheels are connected to each other by 5N₃IP ligands in infinite 2D sheets in the (001) plane, featuring 1D infinite channels within each layer. This MOF is used for the adsorption of methylene blue (MB), rhodamine B (RhB), methyl orange (MO), and Congo red (CR). The adsorption is selective to the dimensions, shapes and ionic strengths of the dyes. Cu(II)–5N₃IP exhibited adsorption rates in the order MB > CR > RhB > MO. Cu(II)–5N₃IP is used as a catalyst for aerobic oxidation and Knoevenagel condensation. 3–10 mol% of Cu–5N₃IP selectively catalyzes the oxidation of benzyl alcohol to benzaldehyde in 9–20 h at 60 °C. In Knoevenagel condensation, the reaction of both unsubstituted and substituted benzaldehydes at room temperature was observed at a very low catalyst loading of 3 mol% of MOF within a short time of 3–60 min. This 2D MOF has proved to be more efficient for dye adsorption and the catalytic applications under investigation (such as alcohol oxidation and Knoevenagel condensation) than its analogous 3D or 0D materials.