Ultrafast water sensing and thermal imaging by a metal-organic framework with switchable luminescence

• Published in: Nature communications Vol. 8; no. 1; pp. 15985 - 10
• Main Authors: Chen, Ling, Ye, Jia-Wen, Wang, Hai-Ping, Pan, Mei, Yin, Shao-Yun, Wei, Zhang-Wen, Zhang, Lu-Yin, Wu, Kai, Fan, Ya-Nan, Su, Cheng-Yong
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30.06.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/638/298/921; Blowing; Dehydration; Detection; Emissivity; Heat detection; Humanities and Social Sciences; Ligands; Luminescence; multidisciplinary; Organic solvents; Photoluminescence; Photons; Science; Science (multidisciplinary); Single crystals; Solvents; Switching; Thermal imaging; Water analysis; Water chemistry; Zinc; Zinc oxide
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms15985

A convenient, fast and selective water analysis method is highly desirable in industrial and detection processes. Here a robust microporous Zn-MOF (metal–organic framework, Zn(hpi2cf)(DMF)(H 2 O)) is assembled from a dual-emissive H 2 hpi2cf (5-(2-(5-fluoro-2-hydroxyphenyl)-4,5-bis(4-fluorophenyl)-1 H -imidazol-1-yl)isophthalic acid) ligand that exhibits characteristic excited state intramolecular proton transfer (ESIPT). This Zn-MOF contains amphipathic micropores (<3 Å) and undergoes extremely facile single-crystal-to-single-crystal transformation driven by reversible removal/uptake of coordinating water molecules simply stimulated by dry gas blowing or gentle heating at 70 °C, manifesting an excellent example of dynamic reversible coordination behaviour. The interconversion between the hydrated and dehydrated phases can turn the ligand ESIPT process on or off, resulting in sensitive two-colour photoluminescence switching over cycles. Therefore, this Zn-MOF represents an excellent PL water-sensing material, showing a fast (on the order of seconds) and highly selective response to water on a molecular level. Furthermore, paper or in situ grown ZnO-based sensing films have been fabricated and applied in humidity sensing (RH<1%), detection of traces of water (<0.05% v/v) in various organic solvents, thermal imaging and as a thermometer. Fast and sensitive detection of water molecules in organic solvents and gases remains an important challenge. Here, Pan and co-workers design a metal-organic framework capable of ultrafast and reversible water sensing by photoluminescence switching via an excited state intramolecular proton transfer mechanism.