Mo(VI)–Melamine Hybrid As Single-Source Precursor to Pure-Phase β-Mo2C for the Selective Hydrogenation of Naphthalene to Tetralin

Abstract

A white Mo(VI)–melamine hybrid solid precipitated immediately when aqueous solutions of (NH4)6Mo7O24 and melamine were mixed. This hybrid proved to be an efficient single-source precursor for single-phase β-Mo2C. Treating the precursor at 650 °C in either Ar or H2 resulted in molybdenum carbides, with H2 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 β-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 β-Mo2C with high purity.