Functionalized Metal-Organic Framework for Selective Fluorometric Detection of Sodium Dodecyl Sulfate and Vitamin B12 Using MOF@Cotton Composites and Lewis Base-Catalyzed Condensation Reaction

For the first time, a diamine-functionalizedMOF is usedto detect SDS in water and vitamin B-12 in HEPES bufferby fluorescence turn-on and turn-off, respectively. The LOD and detectiontime are lower than the previously documented probes. The probe coulddetect SDS in environmental water samples and vitamin B-12 in bio-fluids. Lewis base-induced catalytic performance of the MOFwas examined toward the condensation reaction with lower time, moreyield, and wide substrate scope. A zirconium-(IV)-based metal-organic framework(MOF) fluorophorecontaining the 2,5-diaminoterephthalic acid (H2BDC-(NH)(2)) linker was synthesized and characterized. The physicochemicallystable, porous (S (BET) = 504 m(2) g(-1)) MOF (1 ') exhibited selectiveand sensitive fluorescence turn-on behavior toward the sodium dodecylsulfate (SDS) surfactant and turn-off response toward vitamin B-12. This is the first ever reported MOF-based dual opticalsensor of SDS and vitamin B-12. Other competitive analytesdid not interfere in the detection of both the analytes. Along withthe lowest ever reported limit of detection (LOD) values (LOD forSDS = 108 nM and LOD for vitamin B-12 = 45.3 nM), 1 ' displayed short response time for SDS (50 s) andvitamin B-12 (5 s) detection. The MOF was able to detectSDS in various real water samples and vitamin B-12 in variousbio-fluids (urine and serum) and pH media. A MOF-coated cotton compositewas fabricated, which displayed a visible color change under UV lighteven after treating it with a nanomolar concentration of both theanalytes. The sensor displayed excellent reusability up to five cyclesof sensing. Various experimental outcomes evidenced that the electrostaticinteraction between the -NH2 groups of the linkerand the -SO3 (-) group of SDS isthe possible reason for the selective SDS sensing. For vitamin B-12, the energy transfer from the probe to vitamin B-12 resulted in fluorescence quenching. In addition, the catalytic performanceof 1 ' was investigated in the condensation reactionbetween benzaldehyde derivatives with cyanoacetamide with high yieldsin ethanol at 70 degrees C. The solid was used for three cycles withno decrease in its activity and selectivity. PXRD and FESEM analysisbefore and after the reaction suggested the retention of the crystallinityof 1 ', thus indicating catalyst stability.