Theoretical design of diatomic catalysts for intermolecular hydrogen transfer between crotonaldehyde and hydrazine

In this work, the reaction mechanism of crotonaldehyde (CRAL) hydrogenation to crotyl alcohol (CROL) over graphitic carbon nitride (g-CN) supported TM-Ru diatomic catalysts with hydrazine as a hydrogen source was systematically studied by using density functional theory (DFT) calculations. The computational results show that hydrazine can achieve efficient hydrogen transfer at TM-Ru dual sites through a cooperative six-membered-ring transition state, with the energy barrier of the rate-determining step being only 1.15-1.21 eV, which is significantly lower than that of organic hydrogen sources such as ethanol and isopropanol (1.70-2.92 eV). Further side-reaction analysis reveals that only Sc-Ru and Ti-Ru can effectively suppress competing reactions such as deoxygenation, decarbonylation, and enolization, thereby achieving optimal selectivity. Electronic structure studies indicate that the d-band center of the metal sites exhibits a good linear correlation with the energy barrier of the rate-determining step of hydrogen transfer, and can serve as a key electronic descriptor for tuning hydrogenation selectivity. A dual-atom catalyst design principle is proposed with the d-band center as the core descriptor, providing a theoretical basis and general mechanistic insights for hydrogen source optimization and the rational design of efficient dual-site catalysts in hydrogen-transfer hydrogenation processes.