MOF-derived Ru@ZIF-8 catalyst with the extremely low metal Ru loading for selective hydrogenolysis of C–O bonds in lignin model compounds under mild conditions

Abstract

Lignin hydrogenolysis to produce chemicals and biofuels is a challenge due to the stable C–O ether bond structure. Metal–organic framework (MOF) materials with excellent structural and chemical versatility have received widespread attention. Herein, a highly dispersed Ru metal anchored in functionalised ZIF-8 was fabricated by a general host–guest and reduction strategy. The Ru@ZIF-8 catalyst with a high specific surface area could efficiently promote the C–O bond cleavage of a variety of lignin model compounds under mild conditions. Compared with previous studies, the extremely low metal Ru loading in the Ru@ZIF-8 catalyst achieved a relatively higher activity. The introduction of Ru metal not only improved the dispersion of Zn metal, but also enhanced the electron density on the Zn surface, suggesting a high catalytic performance. It was more conducive for the Ru@ZIF-8 catalyst to exhibit the C–O bond cleavage activity when in the presence of both H₂ and isopropanol. An investigation of the mechanism revealed that the direct hydrogenolysis of benzyl phenyl ether was the main reaction pathway.