Abstract
Organic room-temperature phosphorescence, a spin-forbidden radiative process, has emerged as an interesting but rare phenomenon with multiple potential applications in optoelectronic devices, biosensing and anticounterfeiting. Covalent organic frameworks (COFs) with accessible nanoscale porosity and precisely engineered topology can offer unique benefits in the design of phosphorescent materials, but these are presently unexplored. Here, we report an approach of covalent doping, whereby a COF is synthesized by copolymerization of halogenated and unsubstituted phenyldiboronic acids, allowing for random distribution of functionalized units at varying ratios, yielding highly phosphorescent COFs. Such controlled halogen doping enhances the intersystem crossing while minimizing triplet–triplet annihilation by diluting the phosphors. The rigidity of the COF suppresses vibrational relaxation and allows a high phosphorescence quantum yield (ΦPhos ≤ 29%) at room temperature. The permanent porosity of the COFs and the combination of the singlet and triplet emitting channels enable a highly efficient COF-based oxygen sensor, with an ultra-wide dynamic detection range (~103–10−5 torr of partial oxygen pressure).
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Data availability
The data supporting the findings of this study are available within the paper and its Supplementary Information files and also from the corresponding authors upon reasonable request. Supplementary crystallographic information files have been deposited with the Cambridge Crystallographic Data Centre (CCDC) under deposition numbers ClPBA: CCDC 2119959 and BrPBA: CCDC 2119960. They can be obtained free of charge from www.ccdc.cam.ac.uk/data_request/cif. Source data are provided with this paper.
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Acknowledgements
This work is supported by a US Army Office of Scientific Research Single Investigator Grant (D.F.P.) and an NSERC of Canada Discovery Grant (D.F.P.). E.H. and C.R. acknowledge FRQNT doctoral scholarships. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. We thank R. Stein (McGill University) for assistance with solid-state NMR spectroscopy, T. Maris (University de Montreal) for X-ray crystallography and A. Jonderian and E. McCalla (McGill University) for access to PXRD measurements. The computational part of this work was enabled, in part, by The Digital Research Alliance of Canada’s compute clusters (https://alliancecan.ca). We are grateful to the Materials Characterization facilities in the Department of Chemistry of McGill University (MC2) and the McGill Institute for Advanced Materials (MIAM) and the Facility of Electron Microscopy Research at McGill.
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E.H. and D.F.P. conceived the project and wrote the Paper. E.H. and Y.T. prepared and characterized the starting materials and COFs. E.H. and C.R. conducted the photoluminescence measurements. C.-H.L. performed the TEM and HAADF mapping. H.M.T. determined the BrPBA crystal structure and performed thermal analysis and Hirshfeld surface analysis. All authors contributed to data analyses and provided comments on the paper. Correspondence and requests for materials should be addressed to D.F.P.
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Crystallographic data for ClPBA; CCDC reference 2119959.
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Crystallographic data for BrPBA; CCDC reference 2119960.
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Hamzehpoor, E., Ruchlin, C., Tao, Y. et al. Efficient room-temperature phosphorescence of covalent organic frameworks through covalent halogen doping. Nat. Chem. 15, 83–90 (2023). https://doi.org/10.1038/s41557-022-01070-4
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DOI: https://doi.org/10.1038/s41557-022-01070-4
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