Engineered transition metal dichalcogenides in the removal of organic pollutants and heavy metals for wastewater remediation: Synthesis, mechanisms, and global research trends

Transition metal dichalcogenides (TMDs) represent an intriguing family of layered two-dimensional nanomaterials, which have been recently considered as a potential material system for wastewater decontamination due to their unique structural, physicochemical, and surface characteristics. These advantages include specific surface area, tailored electronic structure, phase diversity, plentiful active sites, and facile functionalization that make them very promising candidates as advanced adsorbents for the adsorption of hazardous contaminants from aqueous media. Unlike previous reviews that broadly discuss the multifunctional applications of TMDs, this review exclusively focuses on adsorption-based wastewater remediation, providing a critical analysis of how crystal phases, defect engineering, and synthesis strategies influence adsorption performance and mechanisms. Although TMDs have demonstrated considerable potential, their application in adsorption remains relatively underexplored compared with conventional adsorbents such as activated carbon, metal oxides, and graphene-based materials, highlighting significant opportunities for future research. This review comprehensively summarizes the recent advances in TMD-based adsorbents for the removal of dyes and heavy metal ions, with particular emphasis on pristine and hybrid materials including MoS 2 , WS 2 , WSe 2 , and their heterostructures. The influence of structural properties, phase behavior, and top-down and bottom-up synthesis approaches on adsorption efficiency is critically discussed. Furthermore, the fundamental adsorption mechanisms, including electrostatic attraction, hydrogen bonding, ion exchange, coordination interactions, π-π interactions, and physical adsorption, are systematically analyzed. A bibliometric assessment is also presented to identify global research trends, leading contributors, and emerging research directions in TMD-based adsorption. Finally, current challenges, including phase instability, nanosheet restacking, limited studies on real wastewater, and environmental concerns, are critically evaluated, and future perspectives toward scalable synthesis, defect engineering, composite design, and industrial implementation are proposed. This review provides a comprehensive and critical framework for understanding adsorption using TMDs and offers practical guidance for the rational design and large-scale development of next-generation TMD-based adsorbents for wastewater purification.