Polymeric Particles as Pickering Interfacial Catalysts for Efficient Selective Oxidation of 5–Hydroxymethylfurfural

Selective oxidation of biomass compounds is one of the most important routes for the synthesis of high-value-added chemical intermediates, but multiple oxidation products are often generated during the oxidative process, resulting in poor selectivity. In this work, we construct raspberry-like amphiphilic polymeric nanoparticles by regulating the proportions of hydrophilic and hydrophobic monomers during polymerization using excess surfactant-stabilized microemulsion as templates. Next, the precursor on the surface of the polymers is converted to reactive 2,2,6,6-tetramethylpiperidoxyl (TEMPO) through a post-oxidation procedure to obtain a polymeric catalyst. Such amphiphilic polymer particles are used as efficient interfacial catalysts in an oil–water biphasic system, which can be tightly adsorbed at the biphasic interfaces to construct a Pickering emulsion system for improving catalytic efficiency. As a result, this TEMPO-mediated oxidation reaction resulted in >99.0% conversion of 5-hydroxymethylfurfural (HMF) with >99.0% selectivity toward 2,5-diformylfuran (DFF). Moreover, this interfacial catalytic system exhibited a high turnover frequency (TOF) value of 5.75 min–1, which outperformed superior catalytic activity compared to the reported results. At the end of the reaction, the CO2-responsive polymeric catalyst can be recovered and used for subsequent oxidation runs. This polymer-based Pickering emulsion system provides a promising route for the selective oxidation of high-value-added biomass compounds.