Green and Selective Oxidation of Benzyl Alcohol to Benzaldehyde over Transition Metal LDH Nanosheets: Combining Experiments and DFT Calculations

The solvent-free and aerobic oxidation of benzyl alcohol is an exceptionally efficient approach for synthesizing benzaldehyde; however, the conversion rates and selectivity are still insufficient as effective catalysts need to successfully activate both the O–H bond and the O 2 molecules. In this study, various layered double hydroxides (LDHs) were successfully prepared and employed for the oxidation of benzyl alcohol in a solvent-free environment. The specific LDHs employed in this study comprise Cu–Co–Fe–LDH (I), Zn–Co–Fe–LDH (II), Zn–Ni–Co–Fe–LDH (III), and Cu–Ni–Co–Fe–LDH (IV). The presence of LDH structures in all analyzed samples was verified through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), along with additional techniques such as Raman spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The Cu–Ni–Co–Fe–LDH catalyst exhibited excellent activity in solvent-free benzyl alcohol oxidation, achieving conversions of 7.47% and 12.34% after 5 h, with benzaldehyde selectivity above 99% and 92% under atmospheric and 10 atm O 2, respectively. Density functional theory (DFT) calculations demonstrated that alloying the surface of Cu–Ni–Co–Fe–LDH may stabilize important intermediate adsorbates in the conversion of ph–CH 2 OH to ph–CHO. These catalysts show great potential for the selective conversion of benzyl alcohol into valuable products for chemical and petrochemical applications.