A Highly Stable Yttrium Organic Framework as a Host for Optical Thermometry and D₂ O Detection

The yttrium organic framework (Y_0.89 Tb_0.10 Eu_0.01 )₆ (BDC)₇ (OH)₄ (H₂ O)₄ (BDC=benzene-1,4-dicarboxylate) is hydrothermally stable up to at least 513 K and thermally stable in air in excess of 673 K. The relative intensities of luminescence of Tb³⁺ and Eu³⁺ are governed by Tb³⁺ -to-Eu³⁺ phonon-assisted energy transfer and Tb³⁺ -to-ligand back transfer and are responsible for the differing temperature-dependent luminescence of the two ions. This provides a ratiometric luminescent thermometer in the 288-573 K temperature range, not previously seen for MOF materials, with a high sensitivity, 1.69±0.04 % K^-1 at 523 K. In aqueous conditions, loosely bound H₂ O can be replaced by D₂ O in the same material, which modifies decay lifetimes to yield a quantitative luminescent D₂ O sensor with a useful sensitivity for practical application.