Rationally engineered icosahedral-spindle aluminum-based metal-organic frameworks with dual-state luminescence for on-site detection of ferric ions in food and human serum.

Dual-state emitters (DSEs), which maintain fluorescence in both solution and solid states, are particularly attractive for practical sensing; however, DSE-type metal-organic frameworks (MOFs) remain comparatively underexplored. Herein, we report the rational design of a novel Al-MOF featuring a uniform icosahedral hexagonal spindle morphology and intrinsic dual-state blue luminescence. The material exhibits strong and stable emission in both aqueous and solid phases without the need for external fluorophores or post-synthetic modification. Owing to its favorable photophysical properties and structural stability, the Al-MOF serves as an efficient fluorescent probe for Fe³⁺ detection, where highly selective quenching occurs primarily through an inner filter effect. To translate material performance into practical deployment, we integrated the Al-MOF into a dual-mode sensing platform combining conventional fluorometric analysis with a smartphone-assisted, instrument-free colorimetric readout. The system provides a linear detection range of 5-182.0 µM and a low limit of detection of 0.23 µM. Reliable Fe³⁺ quantification in spiked human serum and food samples further demonstrates the material's applicability, highlighting its potential as a dual-state emissive MOF platform for portable ferric ion monitoring in point-of-care applications.