Preparasion of layered V4AlC3 MAX phase for highly selective and efficient solvent-free aerobic oxidation of toluene to benzaldehyde

Selective and solvent-free aerobic oxidation of toluene as a volatile organic compound to benzaldehyde is of immense industrial significance, which is limited by harsh chemical conditions. Developing novel catalysts for overcoming this limitation has attracted the interest of researchers. In this work, a highly stable two-dimensional V₄AlC₃ MAX phase with layered-like polycrystal structures was synthesized successfully. X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy were applied to assess the structure of the MAX phase catalyst. Moreover, the morphology of the synthesized MAX phase was studied using scanning electron microscopy and transmittance electron microscopy. The prepared multi-layered V₄AlC₃ MAX phase represented a high catalytic activity for solvent-free aerobic oxidation of toluene to benzaldehyde. Up to 18.4% conversion and 84.2% selectivity to benzaldehyde was obtained within only 4 h under air pressure condition. Furthermore, the radical-based mechanism of the oxidation was confirmed by electron paramagnetic resonance by following the produced organic free radical species during reactions.