Acid-base synergistic effect towards catalytic transfer hydrogenation reactions

Catalytic transfer hydrogenation (CTH) of aldehydes/ketones by using alcohols as hydrogen donors is an attractive and environmentally friendly hydrogenation technology, which has evoked widespread attention in synthesis of fine chemicals from biomass resources. In this work, a Co-Al mixed metal oxide catalyst (CoAl-MMO-200) was obtained through structural topological transformation process of layered double hydroxides, which was used in the CTH reaction of furfural with isopropanol. Notably, the reaction rate achieves 0.023 mol g h, which is preponderate to acid-base catalysts earlier reported. The joint research based on CO-TPD, NH-TPD and poisoning experiment substantiates that the synergy effect of acid-base sites plays an essential role in this catalytic system. Isotopic labelling MS, FT-IR and DFT studies further verify that the CTH reaction of furfural occurs the Meerwein-Ponndorf-Verley (MPV) route, in which the basic site promotes the deprotonation of isopropanol whilst the acid site facilitates the formation of a six-membered ring transition state. This work demonstrates an acid-base synergetic catalysis for the CTH reaction by revealing the structure-property correlation and exploring reaction route, which is instructive for designing high-performance heterogenous catalysts.