Polysaccharide Hydration Networks Suppress Pyrophoricity and Preserve Reactivity of Iron Nanoparticles for On-Demand Environmental Remediation

Reactive iron nanoparticles (INP) face critical challenges in environmental applications due to pyrophoric hazards and rapid oxidation. Here, we present an aqueous-phase nanoencapsulation strategy using natural polysaccharides to construct a mechano-responsive hydration network that ensures safe INP storage and controlled deployment. By engineering a polysaccharide-based hydration matrix, we immobilize 30 wt % INP within a noncombustible viscoelastic solid, eliminating pyrophoric risks while achieving <0.5% daily Fe(0) loss and >96% H₂ evolution suppression over 60 days under practical storage and transport conditions─outperforming conventional aqueous slurry in reactivity preservation. Mechanistic studies reveal that the matrix enables dual preservation pathways: (1) microenvironment engineering via 1.1 nm hydrophilic nanoconfinement, which restricts water mobility, increases bound water phases (∼45%), and elevates Fe(0)-H₂O reaction barriers by +1.56/0.93 eV; and (2) autonomous corrosion inhibition through an in situ-formed H₂ coating. The mechano-responsive design facilitates on-demand liberation via shear-driven dissolution, yielding injectable suspensions with enhanced functionality (e.g., colloidal stability, subsurface mobility, and contaminant removal efficiency). Multiscale characterizations─from molecular dynamics simulations to contaminant remediation─validate the approach. This strategy secures the entire INP remediation lifecycle (storage, transport, and injection), establishing an integrated platform that synergizes fundamental water-structure manipulation with autonomously formed gas-phase shielding principles for safe, sustainable nanoremediation.