Misra, Superb K.Superb K.Misra2025-10-222025-10-222025-10-0110.26434/chemrxiv-2025-1c6nzhttps://repository.iitgn.ac.in/handle/IITG2025/33390Metal–organic frameworks (MOFs) hold immense potential for applications from separations to catalysis, yet their long-term behaviour across real-world environments remains unclear. Here we introduce a hierarchical exposure framework that tracks the structural and chemical transformations in the archetypal zirconium MOF UiO-66 across sequential compartments - atmospheric gases, air, aqueous media and a biological host – and resolves how prior exposures condition or prime subsequent transformations. Using synchrotron-based spectroscopy, we find that oxidative gases leave the Zr-carboxylate nodes essentially intact, whereas exposure to environmentally relevant aqueous media initiates partial shifts in local Zr coordination and introduces oxygen into the pores – with transformation extent governed by the chemistry of the environmental matrices. Strikingly, acute exposure (24 h) to the water flea Daphnia magna drives profound framework degradation and re-speciation to a homogeneous biotic Zr species. Microfocus XRF maps show that Zr is highly localized in the animal’s digestive tract, and region-specific XANES confirms uniform speciation across its tissues. Our findings establish a cross-compartment transformation hierarchy in which biological processes can dominate the fate of stable MOFs even when abiotic exposures appear benign. Thus, organism-level biotransformation should be performed as a necessary part of environmental safety assessments and materials design.MOFsHierarchial transformationNanomaterial transformationEnvironmental healthe-Printhttps://doi.org/10.26434/chemrxiv-2025-1c6nz0