A blue luminescent MOF as a rapid turn-off/turn-on detector for H sub(2)O, O sub(2) and CH sub(2)Cl sub(2), MeCN: super(3) sub( infinity )[Ce(Im) sub(3)ImH].ImH

• Published in: Dalton transactions : an international journal of inorganic chemistry 2015-02, Vol.44 (9), p.4070-4079
• Main Authors: Meyer, LV, Schonfeld, F, Zurawski, A, Mai, M, Feldmann, C, Mueller-Buschbaum, K
• Format: Article
• Language: English
• Subjects: Activation; Chromaticity; Detectors; Drying; Liquids; Luminescence; Methyl alcohol; Pyridines
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt03578j

The blue emitting luminescent MOF super(3) sub( infinity )[Ce(Im) sub(3)ImH].ImH forms a 3D-framework with Kagome net topology. The framework exhibits an intense blue luminescence which can be retained upon activation of the MOF with the formula super(3) sub( infinity )[Ce(Im) sub(3)ImH]. The luminescence is metal-based due to parity-allowed 5d-4f-transitions. Time-dependent investigations of the interaction with liquid and gas analytes show that the MOF - by utilising 5d-4f-transitions of Ce super(3+) - can be used as a high-speed "turn-off" detector for water and oxygen in dry air. Other protic or polar solvents, like methanol, acetone or pyridine, which also show a "turn-off"-effect can be distinguished from water-detection either on a time scale (ranging up to 250 000 : 1) or a shift of the chromaticity, the latter being pronounced for MeOH. The fast time-dependent decrease of the luminescence intensity for water arises from an extremely fast hydrolysis and is irreversible. Polar aprotic molecules like dichloromethane and acetonitrile can also result in a "turn-on"-effect of the luminescence intensity due to their behaviour as additional sensitizers for Ce super(3+)-emission. We conclude that the cerium-MOF can be utilised in gas and liquid sensing applications as a detector material for water and oxygen in dry air. The luminescence is intense with good quantum yield between 55% (as-synthesised) and 36% (activated). This implies that only milligram amounts of the material are needed to detect the analyte species and is especially useful, as the MOF can be directly used as-synthesised for water detection in applications for which an irreversible signal change is desired, e.g. preventing a signal change upon unwanted re-drying.