Nanoconfined metastable manganese sulfide in mesoporous silica enables effective suppression of microbial mercury methylation.

Mercury contamination in aquatic ecosystems poses a persistent threat to human health, primarily due to the formation of the highly toxic and bioaccumulative methylmercury (MeHg). Conventional remediation strategies (e.g., adsorption, precipitation) often fail to prevent MeHg generation as the immobilized mercury remains bioavailable to methylating microorganisms. Here, we develop a manganese sulfide-mesoporous silica composite (MnS@SBA) that leverages nanoconfinement within the silica channels to stabilize the metastable γ-MnS phase, thereby enhancing mercury sequestration while effectively suppressing microbial methylation. The MnS@SBA exhibits exceptional Hg(II) sequestration efficiency across diverse environmental conditions (e.g., pH, redox conditions, dissolved organic matter, coexisting ions). Spectroscopic and microscopic analyses, combined with theoretical calculations, reveal that nanoconfinement promotes strong Hg-S interactions and facilitates HgS precipitation within the silica channels, minimizing mercury bioavailability. Crucially, MnS@SBA prevents contact between immobilized mercury and microorganisms, effectively suppressing microbial MeHg production. Composed of low-cost, naturally abundant components and superior performance in simultaneous Hg(II) removal and MeHg suppression, MnS@SBA presents a promising and practical material for mitigating mercury pollution in aquatic environments. This study establishes a novel framework for designing nanoconfined functional materials that simultaneously achieve metal remediation and ecological risk mitigation, offering insights for designing advanced materials targeting heavy metal contaminants.