One-pot synthesis of potassium-loaded MgAl oxide as solid superbase catalyst for Knoevenagel condensation

We report a new strategy for one-pot synthesis of potassium-loaded MgAl oxides using KOH to adjust the pH value of the reaction system. The as-prepared solid superbases were studied by N₂ physisorption method, energy-dispersive X-ray spectroscopy, powder X-ray diffraction, and Fourier transform infrared. The superbasic sites were characterized by the use of Hammett indicators and CO₂ temperature-programmed desorption. We found that with a base strength (H_-) above 26.5, the potassium-loaded MgAl oxides showed high catalytic activity for Knoevenagel condensation at room temperature. Furthermore, the higher the superbasicity and/or the more the amount of superbasic sites, the better is the catalytic activity. The findings open up a new route for the synthesis of new functional superbases using composite oxides as supports.