A Stable Luminescent Covalent Organic Framework Nanosheet for Sensitive Molecular Recognition

Despite rapid advances in fluorescence detectors over the past decade, the development of a highly stable, sensitive, and selective fluorescence platform for molecular recognition remains a considerable challenge. Here we report a stable carbazole-based sp2 carbon fluorescence covalent organic framework (COF) nanosheet, termed a JUC-557 nanosheet. Owing to the synergistic effect of aggregation-induced emission-and aggregation-caused quenching-based chromophores, the architecture of the JUC-577 shows high absolute quantum yields (up to 23.0%) in the solid state and when dispersed in various solvents as well as excellent sensing performance toward specific analytes, such as iodine (Ka: 2.10 x 105 M-1 and LOD: 302 ppb), 2,4,6 -trinitrotoluene (Ka: 4.38 x 105 M-1 and LOD: 129 ppb), and especially nitrobenzene (Ka: 6.18 x 106 M-1 and LOD: 5 ppb) that is superior to that of fluorescence detection materials reported so far. Furthermore, the JUC-557 nanosheet preserves strong luminescence and sensitive recognition, even under harsh conditions, and allows trace detection of various analytes via a handheld UV lamp. These findings pave the way for developing stable ultrathin COF nanomaterials for highly sensitive and selective molecular detection.

Automated summary

A stable carbazole-based sp2 carbon fluorescence covalent organic framework (COF) nanosheet, named JUC-557 nanosheet, was developed for highly sensitive and selective molecular detection. The nanosheet exhibited high absolute quantum yield, excellent sensing performance, and retained strong luminescence and sensitive recognition even under harsh conditions.