Development of RhB@CdMOF-based Fluorescent Sensor Array for Discrimination of BTEX

Benzene, toluene ethylbenzene and xylene (BTEX), known for their high toxicity and volatility, are key targets for air quality monitoring. Fluorescent probes based on the luminescence intensity of one transition is not efficient for probing BTEX. In this work, we have synthesized a luminescent RhB@MOF sensor array to realize the probing of different BETX by excellent fingerprint correlation between the BTEX and emission peak-height ratio of ligand to dye moieties. Three kinds of RhB@MOF were synthesized simultaneously by varying concentrations of Rhodamine B (RhB) in the solvothermal reaction of (E)-4-(2-carboxyvinyl)benzoic acid (H₂L) and Cd(NO₃)₂·4H₂O (RhB@MOF1, RhB@MOF2, RhB@MOF3). These sensors exhibited two characteristic emission peaks at 430 nm for the host CdMOF and 570 nm for guest RhB, and the emission peak height ratio I₄₃₀/I₅₇₀ were constant for each RhB@MOF. Upon reaction with BTEX, due to gap-gap reaction between ligand and different BETX as well as the different swelling effect of BTEX on RhB, the two emission peaks height ratio of three kinds of RhB@MOF showed specific change to different BTEX. The sensor array exhibited a unique pattern of fluorescence variations of BTEX. Principal component analysis (PCA) was applied and achieved complete separation of BTEX. Linear discriminant analysis (LDA) was then applied to discriminate between individual, binary, ternary, and quaternary mixtures of BTEX, resulting in a 100% accuracy rate. Further study also indicated that concentration gradients did not affect the clustering outcomes of BTEX. Compared to traditional methods, the developed fluorescent sensor array offered a more efficient and economical strategy for the identification of BTEX.