Highly stable and sensitive LnMOF ratiometric thermometers constructed with mixed ligands

Abstract

The mixed-lanthanide metal–organic frameworks (M'LnMOFs) applied for accurate, non-invasive and self-reference temperature measurements have been only recently recognized. It is a great challenge for chemists to fulfil the requirements of a thermostable structure, intense luminescence and high temperature sensitivity on one LnMOF ratiometric thermometer for thermometric applications. By choosing 2,4-(2,2′:6′,2′′-terpyridin-4′-yl)-benzenedisulfonic acid (H₂DSTP) as the first ligand and changing the ancillary ligand to oxalic acid (OA) or 1,4-benzene dicarboxylic acid (BDC), we have successfully developed two types of highly stable and sensitive thermometers [Tb_1−xEu_x(OA)_0.5(DSTP)]·3H₂O and [Tb_1−xEu_x(BDC)_0.5(DSTP)]·2H₂O (x = 0.01, 0.02) that in addition exhibit brilliant luminescence over a wide temperature range, providing a new strategy to explore luminescence-based M'LnMOF thermometers.