Tuning of Thermometric Performances of Mixed Eu–Tb Metal–Organic Frameworks through Single-Crystal Coordinating Solvent Exchange Reactions

Abstract

An initial investigation on the employment of targeted structural alterations, achieved through the post-synthesis modification method, for modulation of the thermometric properties of metal–organic frameworks (MOFs) is reported. The MOF Eu0.05Tb0.95-NBDC (NBDC = 2-amino-1,4-benzenedicarboxylate) is chosen as pristine material, and its terminal N,N-dimethylformamide (DMF) molecules are exchanged by various terminal and chelating ligands through a single-crystal-to-single-crystal coordinating solvent exchange reaction. Temperature-dependence luminescence studies reveal that all samples are highly sensitive in the medium range with a maximum relative sensitivity of 2.6% K−1 at 190 K for Eu0.05Tb0.95-NBDC. In addition, a shift of 50 K of the operating temperature range is evidenced for the exchanged analogs. This is attributed to the occurrence of different deactivation pathways in the exchanged analogs due to the presence of N-donor terminal or N/O-donor chelating aromatic ancillary ligands in the place of DMF terminal ligands in the pristine material. Overall, this work provides insights into the role of terminal and chelating ligands on the thermometric properties of mixed Eu–Tb MOFs and proposes a promising strategy to control and modulate their thermometric performances.