Ultrasensitive arginine detection and selective amine discrimination via a dual-emission UiO-67-Ru probe

The detection of amine compounds, including amino acid identification, is pivotal for advancing biological disease surveillance and for evaluating food safety and environmental contamination. Here, the novel photoluminescence(PL) sensor of a ruthenium-based metal-organic framework for aliphatic amines and arginine is reported, with naked-eye distinguishable color changes and ultrahigh sensitivity. A dual-emission UiO-67-Ru metal-organic framework (MOF) engineered through mix-and-match integration of [Ru(bpy)₃]^{2 +} into the UiO-67-bpy framework, which generates two different PL groups under a single backbone. At a low 5 % Ru-doping level, it was found that the UiO-67-Ru displays the most optimized photoluminescence while preserving framework integrity and microscopic morphology. The sensor exhibits dual emission at 380 nm (from the MOF backbone) and 665 nm (from the Ru center), enabling ratiometric detection of aliphatic amines. Specifically, ultrasensitive arginine (Arg) detection was achieved with a limit of detection (LOD) of 0.072 μM, a linear range of 0–10 μM, and a distinct color transition. Selectivity profiling against thirteen nitrogenous species (e.g., lysine, dopamine) shows UiO-67-Ru favors Arg over n-pentylamine by > 5-fold, a bias traced to Lewis acid–base pairing between aliphatic amines and electron-deficient bipyridine linkers. DFT reveals that amines selectively quench the 665 nm emission of [Ru(bpy)₃]²⁺ via weak C–H···N hydrogen bonds; this adduct narrows the MLCT gap and triggers PET, extinguishing red PL. Finally, the sensor maintains greater than 90 % PL intensity after 7-day storage and three sensing cycles, showcasing its practical applicability in complex environments.