Structure–activity relationship in La–Zn, La–Nb, and Zn–Nb mixed oxides synthesized by mechanochemical activation for Claisen–Schmidt condensation

Mixed La–Zn, La–Nb, and Zn–Nb oxides were synthesized by mechanical mixing followed by calcination and characterized by XRD, TGA/DTA, UV–Vis, and FT-IR spectroscopy. The analyses confirmed the formation of mixed oxide systems with strong interactions between the component oxides. Acid–base properties determined by NH 3 -TPD and CO 2 -TPD showed that the LaZnO x (1:1) sample possesses the highest concentration of surface active sites and a balanced acid–base character. Catalytic activity was evaluated in the solvent-free Claisen–Schmidt condensation of benzaldehyde with acetophenone. Mixed oxides exhibited higher activity than the corresponding single oxides, with LaZnO x (1:1) achieving the highest chalcone yield (85% after 4 h of reaction) and excellent stability upon reuse. The superior performance of LaZnO x (1:1) is attributed to the synergistic interaction between La 3 + and Zn 2+ species, which generate cooperative acid–base sites on the surface. These results demonstrate the potential of LaZnO x mixed oxides as efficient and reusable bifunctional catalysts.