Cu(II)-Doped ZIF-8 as a Sustainable Catalyst for the Dehydrogenative Coupling of 2-Aminobenzamide with Methanol

In this study, an effective and stable Cu²⁺ incorporated within the lattice of ZIF-8 was hydrothermally synthesized and employed as a heterogeneous catalyst for the dehydrogenative coupling between 2-aminobenzamide and CH₃OH. The Cu²⁺-doped ZIF-8 (Cu@ZIF-8) catalysts were firmly characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-visible diffuse reflectance spectra, and Brunauer-Emmett-Teller techniques to examine their structural, morphological, elemental, optical, and surface properties. The catalytic efficiency of Cu@ZIF-8 was investigated in the synthesis of quinazolinone from 2-aminobenzamide and CH₃OH as a C1 source with Cs₂CO₃ as a base under an oxygen atmosphere. Among the different catalysts, 30% Cu@ZIF-8 catalyst demonstrated superior activity in the formation of quinazolinone compared to pristine ZIF-8, indicating that the doping of the Cu²⁺ ions provides a synergetic effect during the reaction. Furthermore, reusability experiments were carried out with a 30% Cu@ZIF-8 catalyst, and the observed findings show that the activity is maintained up to four cycles. The structural integrity along with the morphology and chemical structure of the reused solid were also verified, and no significant differences between the fresh and reused solids were observed in the dehydrogenative coupling reaction. Furthermore, a plausible reaction mechanism for this reaction is also proposed.