One-step reductive amination of 5-hydroxymethylfurfural to 2,5-bis(ami-nomethyl)furan over a core-shell structured catalyst

2,5-Bis(aminomethyl)furan (BAF) is a diamine that is expected to have extensive applications in organic synthesis, medicine and polymer materials such as polyamides and polyimides. BAF can be prepared by one-step reductive amination of 5-hydroxymethylfurfural (HMF), one of the platform compounds for the added-value conversion of biomass. Due to its complex structure, the one-step catalytically reductive amination of HMF to BAF in high yield is still a challenging issue. Herein, a core-shell structured catalyst (Ni@SiO2-0.2) was developed for this reaction, and the yield of BAF reached up to 99 % with aqueous ammonia as both ammonia source and solvent due to an isolation effect of the SiO2 shell. The isolation effect can prevent direct hydrogenation of HMF and self-coupling of BAF, thereby enhancing the selectivity of the reductive amination of HMF to BAF. In addition, the textural structure, acidity and acidic sites of the SiO2 shell can be tuned by adjusting the amount of TEOS during the catalyst preparation process, thus optimizing the performance of the catalyst. The characterization results also revealed that the Ni nanoparticles in the catalyst are uniformly dispersed and encapsulated within the SiO2 shell, which can decrease the charge density on the Ni surface and enhance the adsorption of ammonia and intermediates on the Ni surface, thus enhancing the catalytic activity of the catalyst.