Europium Metal–Organic Framework Polymer Composites with Enhanced Luminescence and Selective Ferric Ion Sensing

Abstract

Ferric ions (Fe 3+ ) play an important role in various biological and chemical processes in living organisms, natural environments, and industry. To understand these roles, a fast and accurate sensor for the selective detection and quantification of Fe 3+ is highly desirable. Herein, we report the development and assessment of a luminescent europium metal−organic framework (MOF, with specific acronym EuMTA, named for the ligand used in the synthesis: 2-methoxyterephthalic acid)�polymer composite material. Immobilizing EuMTA within a cross-linked poly(2hydroxyethyl methacrylate) (PHEMA) matrix resulted in a significant enhancement in the ligand-Eu antenna effect, as well as an increase in the Fe 3+ sensing range (detection of Fe 3+ at concentrations between 2 and 120 ppm) compared to native EuMTA powder (0.16−4 ppm). The PHEMA matrix also functioned to protect the embedded MOF, improving the stability of the sensor under acidic conditions, while enhancing Fe 3+ ion selectivity compared to a EuMTA powder suspension. The MOF-composite sensor exhibited excellent luminescence intensity, stability over prolonged storage (21 days), and reusability. Furthermore, the application of the MOF-composite sensor for mineral processing was successfully demonstrated by monitoring Fe 3+ concentrations using a simulated mineral leaching model.