Transition metal carbides (TMCs) have demonstrated outstanding potential for utilization in a wide range of catalytic applications because of their inherent multifunctionality and tunable composition. However, the harsh conditions required to prepare these materials have limited the scope of synthetic control over their physical properties. The development of low-temperature, carburization-free routes to prepare TMCs would unlock the versatility of this class of materials, enhance our understanding of their physical properties, and enable their cost-effective production at industrial scales. Here, we report an exceptionally mild and scalable solution-phase synthesis route to phase-pure molybdenum carbide (alpha-MoC1-x) nanoparticles (NPs) in a continuous flow millifluidic reactor. We exploit the thermolytic decomposition of Mo(CO)(6) in the presence of a surface-stabilizing ligand and a high boiling point solvent to yield MoC1-x NPs that are colloidally stable and resistant to bulk oxidation in air. To demonstrate the utility of this synthetic route to prepare catalytically active TMC NPs, we evaluated the thermochemical CO2 hydrogenation performance of alpha-MoC1-x NPs dispersed on an inert carbon support. The alpha-MoC1-x/C catalyst exhibited a 2-fold increase in both activity on a per-site basis and selectivity to C2+ products as compared to the bulk alpha-MoC1-x analogue.