Gallium‐Based Eutectic Alloys as Liquid Electron Donors to Ruthenium Single‐Atom Catalysts for Selective Hydrogenation of Vanillin

Abstract Tuning the catalytic pathways of atomically dispersed single‐atom catalysts (SAC) has emerged as an effective strategy to optimize their overall catalytic activity. Herein, we present Ru 1 @m‐tube, a hollow carbon nitride‐supported Ru SAC, coated with eutectic galinstan (GaInSn), as a model catalyst, we demonstrate a performance inversion in vanillin conversion. Vanillin, as a biomass‐derived compound with industrial relevance, presents challenges in catalytic hydrogenation, making it an ideal model reaction to test and compare the catalyst's selectivity and efficiency. The as‐obtained Ru 1 @m‐tube(GaInSn) achieved nearly 100% vanillin conversion within 5 h and exhibited an impressive 93.8% selectivity for vanillyl alcohol. Electron spillover from gallium‐based eutectic alloys to highly diluted ruthenium sites enhances the desorption of vanillyl alcohol, resulting in an exceptional performance shift between hydrogenation and hydrodeoxygenation. Our findings not only offer a novel approach for modulating SAC performance via liquid–metal interfaces but also expand the understanding of promoter screening for various challenging reactions.