A stable luminescent covalent organic framework nanosheet for sensitive molecular recognition

24 May 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Despite the rapid development of fluorescence detectors over the past decade, it still remains a considerable challenge to exploit a highly stable, sensitive, and selective fluorescence platform for molecular recognition. In this study, we report a stable carbazole-based sp2 carbon fluorescence covalent organic framework (COF) nanosheet, termed JUC-557-nanosheet. Owing to the synergistic effect of AIE- and ACQ-based chromophores in JUC-557-nanosheet, this architecture shows high absolute quantum yields (up to 23.0%) in solid state and the dispersed in various solvents and excellent sensing performance toward specific analytes, such as iodine (Ka: 2.10  105 M-1 and LOD: 302 ppb), 2,4,6-trinitrotoluene (Ka: 4.38  105 M-1 and LOD: 129 ppb), and especially nitrobenzene (Ka: 6.18  106 M-1 and LOD: 5 ppb), which is superior to those of fluorescence detection materials reported so far, including porous materials, small molecule probes and inorganics. Furthermore, its fluorescence quenching mechanism has been demonstrated to be a synergistic effect of static quenching and energy transfer quenching by a combined theoretical and experimental study, including time-resolved photoluminescence measurements, UV-vis absorption spectroscopy, and density functional theory calculations. As a chemically stable material, JUC-557-nanosheet preserves strong luminescence and sensitive recognition even under harsh conditions (such as strong acid with pH = 1 or strong base with pH = 14), and allows trace detection of various analytes via a handheld UV lamp. Therefore, these findings pave the way for developing stable ultrathin COF nanomaterials for highly sensitive and selective molecular detection.


covalent organic framework
molecular recognition

Supplementary materials

Supporting Information File
Materials and methods; Characterization; Fluorescence detection; References


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