Fabrication of a carbon quantum dots-immobilized zirconium-based metal-organic framework composite fluorescence sensor for highly sensitive detection of 4-nitrophenol

Metal-organic framework-based composite nanomaterials usually exhibit synergetic properties of their components leading to new functionalities and can be used for a wide range of applications. In this study, we designed and synthesized an amine-CQDs@UiO-66 composite fluorescence sensor by integrating amine-functionalized carbon quantum dots (amine-CQDs) and the zirconium-based metal-organic framework UiO-66 using a post-synthetic modification approach (PSMA). Herein, UiO-66 was used as an adsorbent to capture and enrich the target molecules selectively and the amine-CQDs were employed as a functional monomer to selectively and sensitively sense the bonding interactions between UiO-66 and the target molecules, and further transduce these chemical events into detectable fluorescence signals. The resulting amine-CQDs@UiO-66 sensor exhibited excellent fluorescence selectivity and sensitivity toward 4-nitrophenol (4-NP) because of the immobilized highly fluorescent amine-CQDs. The fluorescence sensitivity was increased because of the enrichment of 4-NP that originated from the well-defined microporous MOF. Moreover, 4-NP could be detected in a wide concentration range of 0.01-20.0 mu M with a detection limit as low as 3.5 nM. To the best of our knowledge, this work presents the first combination of the fluorescence functional monomer amine-CQDs with the favorable properties of MOFs by PSMA for selective fluorescence sensing.