Green strategies for MXene synthesis: Toward sustainable nanomaterials and emerging applications

MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, have attracted significant attention due to their high electrical conductivity, tunable surface chemistry, and structural adaptability. Conventional synthesis routes often rely on corrosive reagents such as hydrofluoric acid (HF), raising environmental and safety concerns. In this review, emerging green synthesis strategies are systematically examined, including electrochemical, alkali-based, molten salt, chemical vapor deposition, Photo–Fenton, physical, and biogenic approaches. Reaction parameters, precursors, reagents, and resulting surface terminations are discussed in detail. Beyond descriptive coverage, a novel analytical framework, the Green Synthesis Index (GSI), is introduced to quantitatively evaluate each route against sustainability-driven metrics such as safety, scalability, energy demand, environmental impact, termination diversity, and application suitability. The decision matrix derived from this framework indicates that electrochemical etching achieves the highest overall scores, while molten salt, physical, and biogenic methods excel in environmental compatibility but face scalability challenges. Chemical vapor deposition offers unmatched structural precision yet suffers from high energy demand, whereas Photo–Fenton protocols provide benign chemistry but require optimization for industrial translation. By consolidating these insights, the GSI transforms MXene synthesis from a descriptive catalog into a decision-making paradigm, enabling systematic prioritization of routes tailored to specific applications. Overall, green synthesis pathways, when assessed through the GSI framework, provide viable and scalable alternatives to conventional methods, aligning MXene development with global sustainability goals while opening new opportunities for safe and application-oriented material design.