A white Mo(VI)-melamine hybrid solid precipitated immediately when aqueous solutions of (NH4)(6)Mo7O24 and melamine were mixed. This hybrid proved to be an efficient single-source precursor for single-phase beta-Mo2C. Treating the precursor at 650 degrees C in either Ar or H-2 resulted in molybdenum carbides, with H-2 being the optimal choice from the perspective of achieving a high-purity carbide. This single-source route successfully inverted the direction of carbon diffusion, thus alleviating the polymerization of carbon species on the carbide surface, which will provide several advantages in catalytic applications. As in the hydrogenation of naphthalene, an ultrahigh selectivity to tetralin was achieved over the resultant beta-Mo2C, and its highly purified surface facilitated a steady state with high conversion. With the characteristics of low cost and nontoxicity, the Mo(VI)-melamine hybrid could serve as a green starting material for obtaining highly crystallized beta-Mo2C with high purity.