MXenes, a class of 2D nanomaterials derived from MAX phases, have emerged as promising materials for energy storage and conversion applications. The synthesis of MXenes typically involves etching the A-site metal from the MAX phase using concentrated HF or in situ generated HF, which is both hazardous and toxic. This review introduces an alternative, universal, and scalable etching method using molten salts, specifically Lewis acid molten salts, to convert MAX phases into MXenes. The review highlights the versatility and advantages of this method, including its general applicability, control over surface terminal groups, and uniform deposition of metal nanoparticles. The process is illustrated through various examples, demonstrating its effectiveness in preparing MXenes with different surface terminations and compositions. The review also discusses the post-synthetic processing of MXenes, such as metal removal and delamination, and provides insights into the future developments in MXene-based materials, particularly in the context of thermal catalysis.MXenes, a class of 2D nanomaterials derived from MAX phases, have emerged as promising materials for energy storage and conversion applications. The synthesis of MXenes typically involves etching the A-site metal from the MAX phase using concentrated HF or in situ generated HF, which is both hazardous and toxic. This review introduces an alternative, universal, and scalable etching method using molten salts, specifically Lewis acid molten salts, to convert MAX phases into MXenes. The review highlights the versatility and advantages of this method, including its general applicability, control over surface terminal groups, and uniform deposition of metal nanoparticles. The process is illustrated through various examples, demonstrating its effectiveness in preparing MXenes with different surface terminations and compositions. The review also discusses the post-synthetic processing of MXenes, such as metal removal and delamination, and provides insights into the future developments in MXene-based materials, particularly in the context of thermal catalysis.