Formyl‐Modified Polyaniline for the Catalytic Dehydration of Fructose to 5‐Hydroxymethylfurfural

Abstract We report an unprecedented solid organic‐base catalyst, formyl‐modified polyaniline (FS‐PAN), for the dehydration of fructose to 5‐hydroxymethylfurfural (HMF) with a high yield of 90.4 mol %. We demonstrate that the nitrogen atoms incorporated between the phenyl rings in the backbone of the polyaniline chain contribute to the basicity of the catalyst. The grafting of electron‐withdrawing formyl groups to the imine nitrogen atoms leads to a significant increase of basicity of the polymer catalyst owing to the greater localization of electrons at the amide nitrogen atom formed. A linear dependence of the yield of HMF on the grafting level of formyl groups in FS‐PAN indicates that the amide acts as the active phase. A possible reaction mechanism for this organic‐base‐catalyzed dehydration reaction is proposed. The side‐reaction of HMF rehydration is inhibited thoroughly, and the condensation of any reaction intermediates to undesirable oligomers is restrained by this base catalyst. This organic‐base catalyst can be recycled completely without loss of activity. This research highlights the first application of a highly effective and stable solid base catalyst for the transformation of renewable carbohydrates into fine chemicals.