Novel neodymium-based porphyrin metal-organic frameworks for dual-mode detection of iron ions

Effective identification of iron (Fe³⁺) ions in the environment and food supplements is essential but challenging. Though traditional single-mode fluorescent sensing methods are user-friendly and sensitive, their accuracy is prone to being affected by external factors. Therefore, it is necessary to propose multi-mode probes to detect Fe³⁺ accurately and effectively in various media. In this study, a novel neodymium-centered lanthanide porphyrin metal-organic framework (NTMNs)-based sensor was designed for the dual-mode detection of Fe³⁺ using fluorescence and UV. NTMNs was rapidly synthesized by microwave synthesis just 10 min using the lanthanide metal neodymium (Nd) as the metal center and 4,4,4,4-(porphine-5,10,15,20-tetrayl)tetrakis (TCPP) as the ligand. A host-guest effect and electrostatic attraction were observed between NTMNs and Fe³⁺, which resulted in weakening of both the fluorescence intensity and UV absorption of the NTMNs, enabling self-calibrating detection using the NTMNs-based Fe³⁺ sensor in two modes within 5 min. Moreover, Fe³⁺ was successfully measured in real water samples with recoveries ranging from 89.8% to 105.4%. Furthermore, by comparing the detection results for the Fe³⁺ content in iron supplements, we confirmed that the difference in detection accuracy between the proposed sensor and the standard inductively coupled plasma-mass spectrometry method is negligible. The feasibility and validity of the NTMNs-based sensor for the detection of Fe³⁺ were demonstrated. In conclusion, this method exhibits promising application for rapidly detecting Fe³⁺ in dual-mode (UV and fluorescence), with self-calibration, high accuracy and sensitivity for environmental pollution, water quality monitoring, and food safety.