Highly sensitive and selective fluorescent sensor based on a multi-responsive ultrastable amino-functionalized Zn(II)-MOF for hazardous chemicals

Abstract A microscale amino-functionalized Zn(II)-MOF, namely [Zn(NH2-bdc)(4,4’-bpy)] (1) (NH2-H2bdc = 2-amino-1,4-benzenedicarboxylic acid and 4,4’-bpy = 4,4’-bipyridine), has been successfully synthesized, structurally characterized and further utilized as multi-responsive fluorescent sensor for highly sensitive and selective detection of Cr(VI) and 2,4,6-trinitrophenol (TNP). Compound 1 features non-porous 5-fold interpenetrated 3D framework with the Lewis basic sites including the uncoordinated amino and carboxylate groups on the framework for anchoring and recognizing the guest. 1 exhibits not only excellent water and thermal stability but also tolerance to acidic and basic media over an extensive pH range of 2–12. This ultrastable material can sensitively and selectively detect Cr2O72− and CrO42− in water based on the luminescent quenching with relatively low limits of detection (2.21 μM for CrO42− and 1.30 μM for Cr2O72−). Moreover, the unprecedented solvent-dependent luminescent response of 1 as a fluorescent probe for high-efficiency TNP detection was observed. Significantly, 1 not only displays high sensitive fluorescent enhancement upon TNP binding in ethanol but also exhibits fluorescent quenching toward TNP in water with very low limits of detection of 4.47 nM and 0.32 μM in ethanol and water, respectively. This work reports the first example of the utilization of MOF as a sensor for the detection of TNP based on dual responsive luminescence. Importantly, 1 can be simply and rapidly regenerated, displaying excellent recyclability after the sensing experiments.