Atomically Dispersed Sn Catalysts toward Selective Oxidation of Furfural to Biodegradable Polymer Monomers

Succinic acid, an important building block in the polymer industry, is conventionally obtained from fossil resources; its manufacture from renewable biomass provides a promising route but remains a significant challenge. Herein, we report a Sn-doped NiO catalyst prepared via a calcination and deposition–precipitation method, which is featured with atomically dispersed Sn atoms anchored onto NiO support. The resulting 1.1 wt % Sn–NiO catalyst exhibits a satisfactory catalytic performance toward furfural oxidation to succinic acid (conversion: >99%; selectivity: 91.2%) using H2O2 as the oxidant, which is superior to other metal oxide catalysts ever reported. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, X-ray absorption fine structure and X-ray photoelectron spectroscopy analyses confirm that the Sn species show an atomic dispersion on the surface of NiO with local electron transfer from Sn to Ni. Both spectroscopy experiment investigations and theoretical calculations verify that the synergistic effect of bimetallic sites (Sn–O–Ni) is of pivotal importance in promoting the activated adsorption of reactants and the occurrence of the reaction: H2O2 undergoes dissociation to generate hydroxyl radicals at the Sn site while the C═O and C–O bonds in the furan ring experience oxidative decarboxylation and a ring-opening reaction at the Ni site adjacent to Sn. This work not only provides an efficient catalyst toward selective oxidation of furfural to succinic acid but also demonstrates a beneficial route to produce biodegradable polyester monomers from biomass resource.