Zn(II)-Based Multivariate, Multicomponent Metal–Organic Framework as a Highly Sensitive Ratiometric Luminescent Sensor for Rhodamine-B in Edibles

The integration of multivariate and multicomponent approaches to design new functional MOFs has been achieved. A series of novel zinc-based multivariate, multicomponent metal-organic frameworks (MM-MOFs) are constructed that exhibit a ratiometric fluorescence response toward rhodamine-B (RhB) characterized by a distinct enhancement of emission at 589 nm and quenching at 478 nm. This emission behavior enabled self-calibrating sensing of RhB at sub-ppm levels in experimental and real-world samples. The presented sensor system showed a linear Stern-Volmer profile and a limit of detection of 0.126 ppm. The Benesi-Hildebrand model, Freundlich isotherm, Hill binding models, and spectral overlap suggested a heterogeneous and cooperative adsorption behavior and a resonance energy transfer mechanism supported by the presence of various hydrogen-bonding and π-π interaction sites in the MM-MOFs. These results demonstrate that integrating established design strategies can yield new functional features in MOFs.