Unravelling the mechanism of water sensing by the Mg2+ dihydroxy-terephthalate MOF (AEMOF-1 ‘)

In this contribution we build upon our previous work on the MOF [Mg(H(2)dhtp)(H2O)(2)]center dot DMAc (AEMOF-1 center dot DMAc) and its activated dry version AEMOF-1 ‘ which has been shown to exhibit excellent luminescence sensing properties towards water in organic solvents. We demonstrate through combined structural and photophysical studies that the observed changes in the fluorescence properties of AEMOF-1 ‘ upon hydration arise from a structural transformation to the mononuclear complex [Mg(H(2)dhtp)(H2O)(5)]center dot H2O (H(4)dhtp = 2,5-dihydroxyterepthalic acid) (1). In the latter complex, excited state intramolecular proton transfer (ESIPT) is strongly favoured thereby leading to enhanced and red shifted emission in comparison to AEMOF-1 center dot DMAc. Powder X-ray diffraction measurements confirmed that complex 1 is identical to the hydrated form of AEMOF-1 center dot DMAc. As in the case of AEMOF-1 ‘, the dry form of complex 1 (1 ‘) is also an effective sensor for the determination of traces of water in tetrahydrofuran (THF). This work demonstrates that the same chromophore may exhibit very different emission properties when it exists in different chemical environments and that these transformations may be controlled and utilized in water sensing applications

Unravelling the mechanism of water sensing by the Mg 2+ dihydroxy-terephthalate MOF ( AEMOF- 1′)

International audienceThe amorphous compound [Mg(H 2 dhtp)(H 2 O) 2 ] 1′ was shown to be a highly efficient and reusable luminescent sensor for the detection of water in THF, due to its transformation to the strongly emissive complex [Mg(H 2 dhtp)(H 2 O) 5 ]·H 2 O 1

A microporous Mg2+ MOF with cation exchange properties in a single-crystal-to-single-crystal fashion

We report herein a new alkaline earth metal ion organic framework [Mg-2(NH2BDC)(2)(HNO3)]center dot 9H(2)O (AEMOF-7), which shows a 3-D microporous structure with several unusual features, such as the rare trigonal prismatic coordination geometry of one of the crystallographically unique Mg-2(+) centers and the existence of a bridging HNO3 ligand. The H+ ions of the HNO3 ligand are dissociable as demonstrated via proton conductivity measurements. AEMOF-7 displays relatively high selectivity for CO2 vs. CH4 and negligible N-2 uptake. Interestingly, this compound was found to be capable of single-crystal-to-single-crystal (SCSC) exchange of Mg2+ by Cu2+ ions, which was observed for the first time in a MOF material. AEMOF-7 is also luminescent and its photophysical properties were investigated via solid state UV-Vis, steady-state and time-resolved luminescence studies