Cu–Ce Bimetallic Oxide Catalyst Regulates the Intermolecular Hydrogen Transfer Reaction of 5-Hydroxymethylfurfural

The selective transformation of 5-hydroxymethylfurfural (HMF) into valuable compounds such as 2,5-diformylfuran (DFF) and 2,5-dihydroxymethylfuran (DHMF) without using external redox agents presents a promising approach. In this research, a new, cost-efficient copper–cerium bimetallic oxide catalyst (Cu1Ce5/γ-Al2O3) was developed to catalyze the intermolecular hydrogen transfer reaction of HMF, facilitating the production of DFF and DHMF. Here, HMF serves dual roles: as a hydrogen donor, undergoing dehydrogenation to supply hydrogen, and as a hydrogen acceptor, undergoing hydrogenation to produce DHMF. This process enables a safe and effective utilization of hydrogen atoms. The catalyst was analyzed using various analytical techniques, including TEM, XRD, XPS, BET, H2-TPR, and FT-IR. The analyses and density-functional theory (DFT) simulations revealed that the creation of Cu–O–Ce interfacial sites enhances the activation of C–OH and C═O groups in HMF. This enhancement provides bifunctional catalytic active sites for dehydrogenation and hydrogenation in the intermolecular hydrogen transfer reaction of HMF. Under optimal reaction conditions (140 °C, 12 h), DFF and DHMF were produced simultaneously with a molar ratio of 1:1. The HMF conversion rate reached 37.1%, with DFF and DHMF selectivities at 46.6% and 46.1%, respectively. Moreover, recovery experiments indicated that the catalyst maintained good stability after five cycles, with the DFF/DHMF molar ratio consistently close to one. This demonstrates a safe and cost-effective method for the simultaneous production of DFF and DHMF through the intermolecular hydrogen transfer reaction of HMF, without the need for external redox agents.