Insight into the morphology-dependent CeO2 for oxidation of lignin model compounds via C–C bond cleavage

The oxidation of lignin model compounds to esters via C–C bond cleavage has attracted considerable attention, as esters could be used as important polymer precursors and pharmaceutical intermediates. However, most studies focus on designing homogeneous or noble metal catalysts and conducting the reactions under basic conditions. Here, we report an efficient process for the C–C bond cleavage of lignin model compounds and selectively producing esters over different shaped CeO 2 (i.e., nanospheres (S), nanorods (R), nanoparticles (P), and nanocubes (C)) under base-free conditions. Specifically, the yield of methyl anisate from the aerobic oxidation of 1-(4-methoxyphenyl)ethanol reaches 77.6% over CeO 2 -S in one hour (91% in 9 h), exhibiting higher performance compared to other evaluated CeO 2 catalysts (6.4%–40.2%). Extensive characterizations and experimental investigations reveal that the density of weak base sites and oxygen vacancies on the CeO 2 surface is positively correlated with the yield of methyl esters. Furthermore, the reaction pathway is investigated, which confirms that 1-(4-methoxyphenyl)ethanol first undergoes two reactions (i.e., etherification and dehydrogenation) to produce intermediates of 1-methoxy-4-(1-methoxy-ethyl)-benzene and 1-(4-methoxyphenyl)ethanone, respectively, followed by a series of functional group transformations to generate the targeted methyl anisate ultimately. Graphical abstract