Selective aerobic oxidation of aromatic alcohols is pivotal in valorization. However, current catalysts suffer from low aldehyde selectivity, which severely restricts their scalable application and sustainable utilization. High-entropy oxides (HEOs), endowed with flexible electronic structures and tunable defect chemistry, offer promising opportunities to surmount these limitations. However, the structure-activity relationships governing the selective conversion of alcohols-derived substrates remain poorly elucidated. Herein, we design a defect-rich spinel-type high-entropy oxide (HE-NiFe2O4) via a solvent-free mechanochemistry synthesis route, and demonstrate its high catalytic efficiency and excellent aldehyde selectivity in the solvent-free aerobic oxidation of benzyl alcohol-a typical representative of lignin-derived aromatic alcohols-as well as a series of alcohols -related substrates. Mechanistic investigations reveal a trisynergistic catalytic ensemble consisting of oxygen vacancies (Ov), electron-rich Mn sites and electron-deficient Fe sites; this active system cooperatively lowers the activation barriers for O-H and C-H bond cleavage and facilitates the preferential activation of O2. As a result, HE-NiFe2O4 achieves an ultrahigh turnover frequency (TOF ≈ 7224 h-1), nearly quantitative aldehyde selectivity, and remarkable recyclability over multiple catalytic cycles under solvent-free and base-free conditions. This work highlights a defect-driven active site design strategy for sustainable catalytic upgrading of forest-derived bioresources to high-value bioproducts.
Chen et al. (Wed,) studied this question.