Integrated catalyst‐reactor design for benzylic C‐H oxidation: NiCo₂O₄ nanoarrays on metal foam in continuous flow

The selective oxidation of benzylic C‐H bonds to aryl ketones and alcohols holds significant importance in fine chemical synthesis. This study introduces a continuous‐flow aerobic oxidation strategy employing nickel foam‐supported NiCo 2 O 4 spinel oxides as highly efficient heterogeneous catalysts. Prepared via electrodeposition, the catalysts feature nanosheet arrays (~5 nm thick), enabling efficient diffusion of liquid‐phase substrates into the solid catalyst. In a micro‐packed bed reactor, the open‐cell nickel foam, with (~160 μm pores), enhances gas–liquid mass transfer. This strategy achieved >96% fluorene oxidation conversion and >98% selectivity within a short residence time (48 min), with stable performance over 130 h. The method was successfully applied to 13 diverse benzylic C–H substrates. Mechanistic studies indicate a radical‐based pathway, with oxygen adsorption following the Langmuir–Hinshelwood model. Cobalt sites promote oxygen activation, while nickel sites enhance substrate adsorption. This work presents a safe and efficient approach, offering prospects for industrial applications.