Chemistry of Transition Metal Dichalcogenides: Environmental Behaviors Governed by Metal--Chalcogen Bonding

Transition metal dichalcogenides (TMDs), including MoS 2 , MoSe 2 , MoTe 2 , and WS 2 , have emerged as a versatile class of two-dimensional (2D) materials for environmental applications, spanning pollutant capture, water purification, air remediation, chemical sensing, and catalytic conversion. Their high surface-to-volume ratios and tunable electronic properties enable their use as adsorbents for heavy metals and greenhouse gases, sensing platforms capable of ppb–ppt detection of toxic species such as NO 2 , SO 2 , and NH 3 , and catalytic materials for green energy technologies, including the photocatalytic and electrocatalytic conversion of CO 2 into value-added products. However, practical implementation remains limited by challenges in controlling sheet morphology and defect populations, which critically influence reactivity, selectivity, and long-term stability. Here, we present a bonding-centric perspective that links the environmental behavior of TMDs to the chemistry of the metal-chalcogen bond. We show that systematic variations in bond strength, polarity, and charge redistribution across the MoX 2 (X = S, Se, Te) series govern interactions at environmental surfaces and interfaces, including pristine basal planes, defect-engineered systems, and intercalated multilayer structures. These differences dictate adsorption strength, charge transfer, and catalytic pathways for environmentally relevant species, providing a framework expected to extend to other hexagonal TMD families, including WX 2 . By unifying these effects within a single mechanistic framework, this Perspective provides a chemically grounded basis for interpreting the behavior of TMD environmental surfaces and interfaces, while enabling more predictive materials selection and rational design. In doing so, it outlines a pathway toward next-generation environmental technologies that support climate action and sustainable resource management.