Lanthanide-based metal-organic frameworks as luminescent sensors of atmospheric pollutants Jorge Sangrador-Perez 1, Arturo Gamonal-Crespo 1 , Esther Resines-Urie 1 , Roberta Poloni 2 , Juan Cabanillas-González 1 , José Sánchez Costa 1 1 Fundacion IMDEA nanociencia, C/Faraday 9, Ciudad universitaria Cantoblanco, 28049, Madrid, Spain, 2 Université Grenoble Alpes, CNRS, SIMAP, 38000, Grenoble, France Metal-organic frameworks (MOFs) are crystalline materials with bi- and tri-dimensional frameworks formed by the coordination of metal centres to organic molecules (ligands), which act as bridges for those ions. Such bonding makes MOFs exhibit high porosity and open channels, which are capable of taking up and storing gases and host molecules. Moreover, thanks to a rational choice (in both, metal and organic ligand), MOFs can be designed for specific functionalities [1] , [2] . In this case, the correct selection of the ligand with a suitable functional group allows to obtain MOFs with a intermolecular interaction preference for certain molecules and their consequent detection. Furthermore, the selection of lanthanide ions allows the use of their widely studied photoemission intensity, spectral profiles and lifetimes [3] , [4] . In this way it has been demonstrated how the absorption of host molecules by novel Ln-MOFs leads , in some cases, to a perturbation of their emission spectra, a phenomenon that can be exploited for the detection of certain pollutants, making these materials excellent candidates for chemosensing. We have studied three different pollutant interactions, and in addition to this three different and unprecedent photoluminescent sensing schemes. Thereby, the exposition to 50 ppm of NO2 or SO2 triggers either a decrease in the luminescent emission in the case of the Tb_MOF, but in the case of the Eu_MOF the exposure doesn’t seem to produce a quantitative modification. However, the exposure of both materials to a pure CO2 stream shows that both lanthanides exhibit increased luminescence emission but in different magnitudes. These behaviours show how a different lanthanide ion leads to a different deactivation of the excited state of the lanthanide ion and consequently the possibility to use them as selective sensors for different pollutants.
Figure 1 a) 2,5-bis acetylamido terephtalic acid b) Ln_MOF_1 crystal c) Ln_MOF_1 X-Ray diffraction structure d) Tb_MOF_1 behaviour in NO 2 (50ppm) cycles e) Eu_MOF_1 behaviour in NO 2 (50ppm) cycles f) Tb_MOF_1 behaviour in CO 2 (pure) cycles g) Eu_MOF_1 behaviour in CO 2 (pure) cycles h) Tb_MOF_1 behaviour in SO 2 (50ppm) cycles i) Eu_MOF_1 behaviour in SO 2 (50ppm) cycles. References
1. R. Seetharaj, P. V. Vandana, P. Arya, and S. Mathew, Arab. J. Chem., 2019, 12, 3, 295–315. 2. H. Furukawa, K. E. Cordova, M. O’Keeffe, and O. M. Yaghi, Science, 2013, 341, 6149. 3. S. Ali Akbar Razavi and A. Morsali, Coord. Chem. Rev, 2019, 399, 213023. 4. A. Gamonal et al. J. Phys. Chem. Lett., 2020, 11, 9, 3362–3368.
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