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Linkages Make a Difference in the Photoluminescence of Covalent Organic Frameworks |
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| Authors: | Yue Wang Yuan-Zhe Cheng Ke-Ming Wu Dr. Dong-Hui Yang Prof. Dr. Xin-Feng Liu Dr. Xuesong Ding Prof. Dr. Bao-Hang Han |
| Affiliation: | 1. CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190 Beijing, China University of Chinese Academy of Sciences, 100049 Beijing, China These authors contributed equally to this work. Contribution: Data curation (lead), Writing - original draft (lead);2. CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190 Beijing, China University of Chinese Academy of Sciences, 100049 Beijing, China These authors contributed equally to this work. Contribution: Data curation (equal), Writing - review & editing (equal);3. CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190 Beijing, China University of Chinese Academy of Sciences, 100049 Beijing, China Contribution: Formal analysis (supporting);4. CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190 Beijing, China |
| Abstract: | Covalent organic frameworks (COFs) with structural designability and tunability of photophysical properties enable them to be a promising class of organic luminescent materials by incorporating well-designed fluorescent units directly into the periodic skeletons. The photophysical properties of COFs are mainly affected by the structural features, which determine the conjugation degree, charge delocalization ability, and exciton dynamics of COFs. To understand the relationship between COF structures and their photophysical properties, two COFs with the same pyrene chromophore units but different linkages (imine or vinylene) were designed and synthesized. Interestingly, different linkages endow COFs with huge differences in solid-state photoluminescence quantum yield (PLQY) for imine- and vinylene-linked pyrene-based COFs, which possess PLQY values of 0.34 % and 15.43 %, respectively. The femtosecond-transient absorption spectra and time-dependent density functional theory reveal the different charge-transfer pathways in imine- and vinylene-linked COFs, which influence the exciton relaxation way and fluorescence intensity. In addition, an effective white-light device was obtained by coating the vinylene-linked COF on a light-emitting diode strip. |
| Keywords: | Aggregation-Caused Quenching Charge-Transfer Transition Vinylene-Linked COFs White-Light-Emitting Diode |