Affiliation:
1. Univ. Lille CNRS Centrale Lille ENSCL Univ. Artois UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide F-59000 Lille France
2. Institut Charles Gerhardt Montpellier, UMR-5253 CNRS-UM-ENSCM 1919 route de Mende 34095 Montpellier, Cedex 05 France
Abstract
AbstractThe Zr‐based Metal Organic Framework (MOF) UiO‐66(Zr) is widely employed owing to its good thermal and chemical stabilities. Although the long‐range structure of this MOF is preserved in the presence of water during several days, little is known about the formation of defects, which cannot be detected using diffraction techniques. We apply here 17O solid‐state NMR spectroscopy at 18.8 T to investigate the reactivity of UiO‐66, through the exchange of oxygen atoms between the different sites of the MOF and water. For that purpose, we have selectively enriched in 17O isotope the carboxylate groups of UiO‐66(Zr) by using it with 17O‐labeled terephthalic acid prepared using mechanochemistry. In the presence of water at 50 °C and a following dehydration at 150 °C, we observe an overall exchange of O atoms between COO− and μ3‐O2− sites. Furthermore, we demonstrate that the three distinct oxygen sites, μ3‐OH, μ3‐O2− and COO−, of UiO‐66(Zr) MOF can be enriched in 17O isotope by post‐synthetic hydrothermal treatment in the presence of 17O‐enriched water. These results demonstrate the lability of Zr−O bonds and the reactivity of UiO‐66(Zr) with water.
Funder
H2020 European Research Council
Subject
General Chemistry,Catalysis,Organic Chemistry