The synthesis of renewable fuels and platform chemicals from oxygen-rich biomass, such as lignin, requires the selective removal of oxygen-containing functional groups with green hydrogen. This pivotal process, referred to as hydrodeoxygenation (HDO) and used in the petrochemical industry, has been the subject of intensive research in the past decades. Efficiently achieving this transformation would facilitate the largescale production of bio-based fuels and chemicals, reducing the dependency on fossil resources and contributing to a sustainable circular economy and a closed carbon cycle. Breaking C-O bonds is associated with a significant energy barrier due to their high kinetic and thermodynamic stability, requiring the use of catalysts. Heterogeneous catalysts for HDO often comprise late transition metals -to activate dihydrogen -combined with a group V-VII transition metal, in particular Mo, that are thought to facilitate the activation of the C-O bond because of their oxygen affinity and their ability to introduce Brønsted and/or Lewis acidity. These bifunctionalbimetallic catalysts can lead to enhanced activity compared to the corresponding monometallic materials, suggesting a synergy that is crucial for the desired reactivity. However, the exact role and interplay of the components in these catalysts are still poorly understood and often remain speculative, mainly due to the complexity of these materials. In classical synthetic approaches, metallic nanoparticles of late transition metals (M) are commonly prepared via impregnation techniques, often relying on metal chloride (or nitrate) precursors, possibly leading to contamination or uneven particle formation. While cost and time efficient, these approaches generally afford rather ill-defined materials, with non-uniform distribution of surface sites and particle sizes. This complexity arises from the synthetic process as it involves uncontrolled dissolution and precipitation processes in water. This, in turn, makes it challenging to achieve molecular-level understanding of catalytic processes and to develop informative structureproperty relationships. In that context, surface organometallic chemistry (SOMC) has emerged as a synthetic strategy to generate better-defined catalyst structures using tailored (traceless) molecular precursors that are evenly dispersed on the surface by anchoring onto hydroxy groups (grafting), followed by a post treatment to remove the organic ligands; this approach typically generates smaller nanoparticles and a narrower size distribution. In addition, these materials provide tailored interfaces and compositions, while avoiding the incorporation of undesired elements. In the presented work, we investigate a series of HDO catalysts prepared via SOMC based on the combinations of a transitionmetal, known for their hydrogenation properties (M = Rh, Ir, Ni, Pd, and Pt) and Mo, dispersed on a silica support. Among M-Mo/SiO2, we show that the promotional effect of Mo for HDO of alcohols as prototypical oxygenate substrates is highly efficient with Pt, Rh, and particularly so for Ir, while negligible for Ni, and only observed for tertiary alcohols in the case of Pd. Characterization based on the adsorption of CO and pyridine probe molecules, High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM), and Xray absorption spectroscopy (XAS), performed on the catalysts before and after the HDO reaction and preserved under inert atmosphere, show that Mo is reduced in the presence of the primary metal (M) and incorporated in narrowly dispersed 2-3 nm alloyed nanoparticles, without significant changes in Brønsted or Lewis acidity. Overall, the data point to the importance of a metallic state of Mo and alloy formation, indicating M-Mo phases play a critical role in efficient HDO processes.