<p>Two-dimensional transition metal carbides and nitrides (MXenes) are a class of materials that have drawn substantial attention for their diverse application, particularly in the field of energy storage. These materials are commonly derived from layered ternary solids, MAX phases, through etching processes. Efforts have been made to expand the scope of MXene synthesis beyond these top-down approaches to include bottom-up synthesis. Here we demonstrate a general direct synthetic route for scalable and atom-economic synthesis of various MXenes using different organohalide compounds as precursors for both carbon and surface termination groups. By reacting organochlorides (such as C₂Cl₄, C₂Cl₆ and CH₂Cl₂) or organobromides (CBr₄ and CH₂Br₂) with transition metals, we synthesized a variety of MXenes (Ti₂CCl₂, Ti₂CBr₂, Zr₂CCl₂, Zr₂CBr₂ and Nb₂CCl₂), including a Nb₂CBr₂ MXene phase not accessed by other routes. The use of molecular precursors enables precise control of their reactivity, which allows the direct synthesis of MXene nanostructures. We demonstrate that nanometre-scale MXenes show higher surface reactivity compared with MXenes with micrometre-size flakes.</p><p></p>