Crystalline Zn- and Cu-MOF-2 Metal–Organic Frameworks: Synthesis and Comparative Catalytic Evaluation in Isoamyl Acetate Esterification

Monometallic metal–organic frameworks, MOF-2-Cu and MOF-2-Zn, were synthesized at room temperature and evaluated as heterogeneous catalysts for the esterification of isoamyl alcohol with acetic acid to produce isoamyl acetate. The materials were characterized by X-ray diffraction (XRD), FT-IR spectroscopy, nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The analyses confirmed the formation of crystalline, porous MOF-2 materials, with an additional crystalline phase present in MOF-2-Cu. Catalytic performance was assessed at temperatures ranging from 95 to 115 °C. Both MOFs exhibited substantial catalytic activity, achieving maximum isoamyl alcohol conversions of 54.5% for MOF-2-Cu and 51.1% for MOF-2-Zn at 105 °C. Without a catalyst, conversion and yield did not exceed 22.2% and 16.5%, whereas Amberlyst 16 reached 76.9% and 71.4% at 115 °C, showing higher activity than the MOFs. The highest isoamyl acetate yields were observed at 115 °C, reaching 40.5% for MOF-2-Zn and 42.8% for MOF-2-Cu. Reusability studies indicated that both catalysts retained over 80% of their initial activity after three regeneration cycles. These results underscore the potential of MOF-2-Zn and MOF-2-Cu as heterogeneous catalysts for sustainable esterification processes.