Selective oxidation of 5-hydroxymethylfurfural into 2,5-diformylfuran by TEMPO-assisted magnetic Fe3O4@SiO2@mSiO2-NH2-Cu(II) catalytic system

Abstract

2,5-diformylfuran (DFF) is a multifunctional intermediate, which can be used in drugs, functional polymers, fluorescent materials and surfactants. In this paper, a TEMPO-assisted magnetic Fe3O4@SiO2@mSiO2-NH2-Cu(II) catalytic system was developed for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran. The structure of Fe3O4@SiO2@mSiO2-NH2-Cu(II) was double-layer shell-core spherical structure with uniform ordered mesoporous on the surface, amino groups and Cu were evenly distributed in the outer mesoporous. The catalyst was characterized by FT-IR, TEM, EDS, SEM, XRD, BET and VSM. The effects of reaction conditions were investigated in detail. The conversion of HMF was 98.9% and the highest DFF yield was 92.4% under atmospheric oxygen in toluene solvent. The catalytic activity did not decrease significantly after 5 cycles. The catalytic system had good substrate adaptability for benzyl alcohols and aromatic alcohols with satisfactory yield of corresponding aldehydes (91.3–100%). A possible reaction mechanism was also proposed and found that bis(μ-hydroxy) double copper (II) may be the active reactant in oxidation reaction. The system provides a promising industrialized preparation method for DFF.