Introduction of Organic Dyes into Cadmium(II) MOF for Tunable Light Emission and Highly Sensitive Probing Antibiotics

A honeycomb porous cadmium(II) metal–organic framework {[Cd(L)(H2O)] ⋅ NMP ⋅ 5H2O}n (1, H2L=1‐(4‐carboxyphenyl)‐1H‐pyrazole‐3‐carboxylic acid and NMP=1‐methyl‐2‐pyrrolidinone) was obtained using the solvothermal method. The luminescent molecules rhodamine B (RhB) and fluorescein (FL) were encapsulated in 1 using the immersion method to prepare RhB@1 and FL@1 dual emission composites. Additionally, a series of RhBx/FL1‐x@1 composites with varying luminescence properties were generated by altering the molar ratio of RhB to FL. Furthermore, the photoluminescence of RhB@1 and FL@1 was demonstrated to be caused by photoelectron transfer and fluorescence resonance energy transfer from 1 to the encapsulated guest module. Notably, RhB@1 showed the considerable improvement in fluorescence selectivity and detection limit (10−6 M) for metronidazole and dimetronidazole with remarkable recyclability. This work focuses on the design of a new highly stable dye@MOF fluorescence materials for tunable light emission and highly sensitive detection of metronidazole (MDZ) and dimetronidazole (DMZ) by encapsulating dyes in Cd(II) MOFs through post‐synthesis modification (PSM). The luminescent dyes rhodamine B (RhB) and fluorescein (FL) were selected based on the excellent optical and electronic properties.