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Unveiling the Uncommon Fluorescent Recognition Mechanism towards Pertechnetate Using a Cationic Metal–Organic Framework Bearing N-Heterocyclic AIE Molecules |
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| Authors: | Dr Kang Kang Prof Xing Dai Nannan Shen Rongzhen Xie Prof Xingwang Zhang Prof Lecheng Lei Prof Dr Shuao Wang Prof Chengliang Xiao |
| Institution: | 1. College of Chemical and Biological Engineering, Zhejiang University, 38 Zheda Road, Hangzhou, 310027 P. R. China
Institute of Zhejiang University—Quzhou, 78 Jiuhua Boulevard North, Quzhou, 324000 P. R. China These authors contributed equally to this work.;2. State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X) and, Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, 199 Ren'ai Road, Suzhou, 215123 P. R. China These authors contributed equally to this work.;3. State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X) and, Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, 199 Ren'ai Road, Suzhou, 215123 P. R. China;4. College of Chemical and Biological Engineering, Zhejiang University, 38 Zheda Road, Hangzhou, 310027 P. R. China Institute of Zhejiang University—Quzhou, 78 Jiuhua Boulevard North, Quzhou, 324000 P. R. China;5. College of Chemical and Biological Engineering, Zhejiang University, 38 Zheda Road, Hangzhou, 310027 P. R. China |
| Abstract: | As one of most problematic radionuclides, technetium-99, mainly in the form of anionic pertechnetate (TcO4−), exhibits high environmental mobility, long half-life, and radioactive hazard. Due to low charge density and high hydrophobicity for this tetrahedral anion, it is extremely difficult to recognize it in water. Seeking efficient and selective recognition method for TcO4− is still a big challenge. Herein, a new water-stable cationic metal-organic framework (ZJU-X8) was reported, bearing tetraphenylethylene pyrimidine-based aggregation-induced emission (AIE) ligands and attainable silver sites for TcO4− detection. ZJU-X8 underwent an obvious spectroscopic change from brilliant blue to flavovirens and exhibited splendid selectivity towards TcO4−. This uncommon fluorescent recognition mechanism was well elucidated by batch sorption experiments and DFT calculations. It was found that only TcO4− could enter into the body of ZJU-X8 through anion exchange whereas other competing anions were excluded outside. Subsequently, after interaction between TcO4− and silver ions, the electron polarizations from pyrimidine rings to Ag+ cations significantly lowered the energy level of the π* orbital and thus reduced the π–π* energy gap, resulting in a red-shift in the fluorescent spectra. |
| Keywords: | cationic metal–organic frameworks environmental chemistry fluorescent recognition pertechnetate pyrimidine |