Quinoxaline synthesis via oxidative cyclization reaction using metal-organic framework Cu(BDC) as an efficient heterogeneous catalyst

Abstract

A metal-organic framework Cu(BDC) was synthesized, and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. The Cu(BDC) was employed as an efficient heterogeneous catalyst for the oxidative cyclization reaction between α-hydroxyacetophenone and phenylenediamine to form 2-phenylquinoxaline as the principal product. The optimal conditions involved the use of air atmosphere oxidant in toluene solvent at 100 °C in 3h. In addition, the Cu(BDC) exhibited higher catalytic activity in the quinoxaline synthesis reaction than that of others Cu-MOFs such as MOF-199, MOF-118, and Cu₂(BDC)₂(DABCO), and higher than that of Mn(BDC), and Ni₂(BDC)₂(DABCO). The Cu(BDC) catalyst could be recovered and reused several times without a significant degradation in catalytic activity.