Oxidant-free and metal-free highly-selective catalytic production of vanillic aldehyde through activated carbon fiber-mediated aerobic oxidation

Typically, oxidizing agents (such as H₂O₂) are necessitated for vanillic alcohol (VLA) conversion; nevertheless, intensive consumption of H₂O₂ is required due to the stoichiometric chemistry, and metal catalysts are usually required to improve conversion of VLA by H₂O₂. Nevertheless, for pursuing the goal of sustainability, it would be highly desired to develop an oxidizing agent-free and metal-free process which can selectively oxidize VLA to vanillic aldehyde (VAE). The aim of this study is to propose activated carbon fiber (ACF) as a highly effective catalyst for VLA conversion to VAE without using metals and oxidizing agents. At 120 °C within 30 min, ACF could enable C_VLA = 100% with S_VAE = 100% without using metals/oxidants. The effect of radical scavengers and ESR analyses further reveal that the oxidation of VLA to VAE by ACF could be attributed to reactive oxygen species derived from ACF-mediated aerobic reactions.