One-Step Synthesis of Metastable Mo₂AlB₂ from MoAlB Using Gaseous HCl

Recent studies increasingly highlight the potential applications of MBenes, a novel class of two-dimensional (2D) materials, yet their production remains challenging. In this context, microcrystalline Mo₂AlB₂ (space group Cmmm; a = 3.080(3) Å, b = 11.57(1) Å, and c = 3.149(4) Å), a promising precursor for MoB MBene production, was synthesized in a single-step gas-solid reaction at 450 °C using MoAlB and gaseous HCl. This preparation method, previously utilized for the oxidation of Zintl phases, has been successfully adapted to compounds containing d-block elements, providing a new alternative for exfoliating layered materials in liquid solutions. Scanning electron microscopy analysis revealed homogeneous products with microcrystals exhibiting a nonuniform particle size distribution. At higher temperatures, these evolved into plate-like crystallites with smooth surfaces and etch cavities. This efficient and cost-effective gas-solid reaction shows great potential for large-scale production of a wide range of 2D materials, with significant benefits for catalysis, energy storage, and other applications.